speed
Americannoun
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rapidity in moving, going, traveling, proceeding, or performing; swiftness; celerity: the speed of sound.
the speed of light;
the speed of sound.
- Synonyms:
- hurry, expedition, dispatch, alacrity, fleetness
- Antonyms:
- slowness
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relative rapidity in moving, going, etc.; rate of motion or progress.
full speed ahead.
- Synonyms:
- hurry, expedition, dispatch, alacrity, fleetness
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full, maximum, or optimum rate of motion.
The car gets to speed in just nine seconds.
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Automotive. a transmission gear ratio.
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Photography.
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Also called film speed. the sensitivity of a film or paper to light, measured by an ASA or DIN index, which assigns low numbers to slow film and higher numbers to faster film.
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Also called shutter speed. the length of time a shutter is opened to expose the film or digital sensor inside the camera to light.
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the largest opening at which a lens can be used.
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Slang. a stimulating drug, as caffeine, ephedrine, or especially methamphetamine or amphetamine.
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Informal. a person or thing that is compatible with or typical of one's ability, personality, desires, etc..
My speed is writing postcards on the porch while everyone else is tearing around the tennis court.
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Archaic. success or prosperity.
verb (used with object)
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to promote the success of (an affair, undertaking, etc.); further, forward, or expedite.
- Synonyms:
- favor, facilitate, advance
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to direct (the steps, course, way, etc.) with speed.
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to increase the rate of speed of (usually followed byup ).
to speed up industrial production.
- Synonyms:
- accelerate
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to bring to a particular speed, as a machine.
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to cause to move, go, or proceed with speed.
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to expedite the going of.
to speed the parting guest.
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Archaic. to cause to succeed or prosper.
verb (used without object)
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to move, go, pass, or proceed with speed or rapidity.
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to drive a vehicle at a rate that exceeds the legally established maximum.
He was arrested for speeding.
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to increase the rate of speed or progress (usually followed byup ).
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to get on or fare in a specified or particular manner.
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Archaic. to succeed or prosper.
idioms
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at full / top speed,
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at the greatest speed possible.
We drove down the highway at full speed.
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to the maximum of one's capabilities; with great rapidity.
He worked at full speed.
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up to speed,
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operating at full or optimum speed.
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functioning or producing at an expected, acceptable, or competitive level; up to par.
a new firm not yet up to speed.
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noun
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the act or quality of acting or moving fast; rapidity
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the rate at which something moves, is done, or acts
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physics a scalar measure of the rate of movement of a body expressed either as the distance travelled divided by the time taken ( average speed ) or the rate of change of position with respect to time at a particular point ( instantaneous speed ). It is measured in metres per second, miles per hour, etc
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a rate of rotation, usually expressed in revolutions per unit time
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a gear ratio in a motor vehicle, bicycle, etc
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( in combination )
a three-speed gear
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photog a numerical expression of the sensitivity to light of a particular type of film, paper, or plate See also ISO rating
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photog a measure of the ability of a lens to pass light from an object to the image position, determined by the aperture and also the transmitting power of the lens. It increases as the f-number is decreased and vice versa
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a slang word for amphetamine
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archaic prosperity or success
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quickly
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operating at an acceptable or competitive level
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in possession of all the relevant or necessary information
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verb
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to move or go or cause to move or go quickly
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(intr) to drive (a motor vehicle) at a high speed, esp above legal limits
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(tr) to help further the success or completion of
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slang (intr) to take or be under the influence of amphetamines
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(intr) to operate or run at a high speed
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archaic
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(intr) to prosper or succeed
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(tr) to wish success to
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The ratio of the distance traveled by an object (regardless of its direction) to the time required to travel that distance.
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Compare velocity
Synonym Usage
Speed, velocity, quickness, rapidity, celerity, haste refer to swift or energetic movement or operation. Speed (originally prosperity or success) may apply to human or nonhuman activity and emphasizes the rate in time at which something travels or operates: the speed of light, of a lens, of an automobile, of thought. Velocity, a more learned or technical term, is sometimes interchangeable with speed : the velocity of light; it is commonly used to refer to high rates of speed, linear or circular: velocity of a projectile. Quickness, a native word, and rapidity, a synonym of Latin origin, suggest speed of movement or operation on a small or subordinate scale; quickness applies more to people ( quickness of mind, of perception, of bodily movement ), rapidity more to things, often in a technical or mechanical context: the rapidity of moving parts; a lens of great rapidity. Celerity, a somewhat literary synonym of Latin origin, refers usually to human movement or operation and emphasizes expedition, dispatch, or economy in an activity: the celerity of his response. Haste refers to the energetic activity of human beings under stress; it often suggests lack of opportunity for care or thought: to marry in haste; a report prepared in haste. See rush 1.
Other Word Forms
Derived Forms
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speedernoun
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speedfulnessnoun
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speedingnessnoun
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overspeedverb
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outspeedverb (used with object)
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multispeedadjective
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speedfuladjective
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speedlessadjective
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speedfullyadverb
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speedinglyadverb
Inflected Forms
Nouns
Participles
Conjugated Forms
Present
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speedsimple
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speedssimple
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have spedperfect
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have speededperfect
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has spedperfect
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has speededperfect
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am speedingprogressive
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are speedingprogressive
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is speedingprogressive
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have been speedingperfect progressive
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has been speedingperfect progressive
Past
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spedsimple
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speededsimple
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had spedperfect
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had speededperfect
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was speedingprogressive
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were speedingprogressive
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had been speedingperfect progressive
Future
Etymology
Origin of speed
First recorded before 900; 1965–70 speed for def. 6; (noun) Middle English spede “good luck, prosperity, rapidity,” Old English spēd; cognate with Dutch spoed, Old High German spōt; akin to Old English spōwan “to prosper, succeed”; (verb) Middle English speden “to succeed, prosper, go with speed,” Old English spēdan “to succeed, prosper”; cognate with Old Saxon spōdian, Old High German spuoten
Explanation
Speed most often describes acceleration or a high rate of motion. When something picks up too much speed, it can run off course, like a kid on a bike zooming uncontrollably down a steep hill. Speed can be a noun or verb. As a noun, it's an indicator of pace, as in the speed of a car. As a noun, it's also a drug that keeps you awake, very awake. As a verb, it means to “move along quickly,” like how you speed around on your bike. A fun fact: while speed refers to the distance traveled by an object during a specific amount of time, velocity describes that distance, but in a specified direction.
Vocabulary lists containing speed
Word Generation Science - Measurement
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Conservation of Energy and Energy Transfer - Introductory
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Force and Motion (Mechanics) - Middle School
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
Level 4 refers to a fully self-driving system that requires no intervention from the driver, but is limited to specific areas, weather conditions and speed limits.
From The Wall Street Journal ● Jul. 22, 2026
As odysseys go, it’s very much my speed.
From Los Angeles Times ● Jul. 22, 2026
Because it naturally moves at a fixed speed, it is difficult to delay optical signals or temporarily hold them in place.
From Science Daily ● Jul. 22, 2026
Strong winds and a tinder-dry landscape meant that the fire advanced at frightening speed, devouring large amounts of territory in very little time.
From Barron's ● Jul. 22, 2026
The boat gave a kick of speed and leaped forward in the water—but it was not enough.
From "Impossible Creatures" by Katherine Rundell
Class 1 bikes can reach speeds up to 20 mph, and can be ridden by anyone.
From Los Angeles Times ● Jul. 21, 2026
The disk stretches nearly 800 light-years across, and some of the material inside it is moving at speeds of up to 600 kilometers per second.
From Science Daily ● Jul. 18, 2026
The increased speeds of conveyor belts in meatpacking plants, Mr. Smil notes, make those jobs among the most perilous in existence as measured by worker injuries.
From The Wall Street Journal ● Jul. 13, 2026
A white truck slowly approaches the scene, but after the bison charges the truck the driver speeds off.
From BBC ● Jul. 13, 2026
When we finally pulled into the parking lot, my body had to adjust to sub-light speeds before I could pour myself out of the Smokemobile’s backseat and follow Sohrab to the ticket office.
From "Darius the Great Is Not Okay" by Adib Khorram
As he sped to the scene, he saw that a large motor boat was rapidly sinking.
From Los Angeles Times ● Jul. 17, 2026
In a debate in Parliament on Thursday, a number of MPs called for that process to be sped up - and described ground rents as "money for nothing".
From BBC ● Jul. 7, 2026
Warmer global temperatures don’t seem to have sped up the spread or evolution of primates into new species.
From Science Daily ● Jun. 20, 2026
There’s been some encouraging top-line numbers lately, as existing-home sales in May sped up to the fastest pace seen in 2026.
From MarketWatch ● Jun. 13, 2026
As they sped up the road he wondered how fast a leopard could run.
From "Storm Runners" by Roland Smith
It wasn’t long before USC finally speeded away from Iowa, with Desmond Claude and Saint Thomas taking control to close out the Hawkeyes.
From Los Angeles Times ● Jan. 15, 2025
He says inquiries could also be speeded up if they are placed on a non-statutory rather than statutory footing.
From BBC ● Sep. 15, 2024
But the biggest thing Ghai and his family are doing does not directly involve workers at all: They’ve speeded up and expanded their use of technology, especially AI.
From Los Angeles Times ● May 1, 2024
She stressed it was an independent process and she was not involved directly but added: "I think everybody wants to see that speeded up."
From BBC ● Mar. 14, 2024
Two days later she speeded up considerable, and got brave enough to drive all the way home.
From "Cold Sassy Tree" by Olive Ann Burns
The vehicle, with the blue-and-yellow Ukrainian flag affixed to its top, then smashes through the tyre-and-barricade wall, leaping into the air and speeding on.
From Barron's ● Jul. 22, 2026
These include technical issues in China qualifying, a safety car turning the race on its head in Japan, a retirement while leading in Canada, and the still-unresolved farrago over erroneous pit-lane speeding penalties in Monaco.
From BBC ● Jul. 19, 2026
“And then you hear the ‘Boom!’ and I said, ‘Somebody’s gone,’ because that was a loud boom and they were speeding very fast.”
From Los Angeles Times ● Jul. 14, 2026
It’s a civil offense, not even as bad as a speeding ticket.
From Salon ● Jul. 13, 2026
It skids to a stop, nearly crashing into a pair of kids on bicycles, before making a frantic U-turn and speeding away.
From "South of Somewhere" by Kalena Miller
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
