atmospheric pressure
Americannoun
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the pressure exerted by the earth's atmosphere at any given point, being the product of the mass of the atmospheric column of the unit area above the given point and of the gravitational acceleration at the given point.
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a value of standard or normal atmospheric pressure, equivalent to the pressure exerted by a column of mercury 29.92 inches (760 millimeters) high, or 1013 millibars (101.3 kilopascals).
noun
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The pressure at any location on the Earth, caused by the weight of the column of air above it. At sea level, atmospheric pressure has an average value of one atmosphere and gradually decreases as altitude increases.
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Also called barometric pressure
Closer Look
The weight of the air mass, or atmosphere, that envelopes Earth exerts pressure on all points of the planet's surface. Meteorologists use barometers to measure this atmospheric pressure (also called barometric pressure). At sea level the atmospheric pressure is approximately 1 kilogram per square centimeter (14.7 pounds per square inch), which will cause a column of mercury in a mercury barometer to rise 760 millimeters (30.4 inches). The pressure is frequently expressed in pascals, after the French mathematician and philosopher Blaise Pascal, who studied the transmission of pressure in confined fluids. Subtle variations in atmospheric pressure greatly affect the weather. Low pressure generally brings rain. In areas of low air pressure, the air is less dense and relatively warm, which causes it to rise. The expanding and rising air naturally cools, and the water vapor in the air condenses, forming clouds and the drops that fall as rain. In high pressure areas, conversely, the air is dense and relatively cool, which causes it to sink. The water vapor in the sinking air does not condense, leaving the skies sunny and clear.
Discover More
Normal atmospheric pressure at sea level is about fifteen pounds per square inch. (See barometer.)
Etymology
Origin of atmospheric pressure
First recorded in 1655–65
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.
El Nino warms surface temperatures in the central and eastern equatorial Pacific Ocean, triggering worldwide changes in winds, atmospheric pressure and rainfall patterns, and pushing warmer overall global temperatures.
From Barron's ● Jul. 9, 2026
They have also noticed a drop in atmospheric pressure over the central Pacific compared with the western Pacific.
From BBC ● Jun. 9, 2026
A traditional nuclear power plant uses water to cool the reactor core, but Newcleo’s design would instead use liquid lead, which has a higher boiling point and allows operations at atmospheric pressure.
From The Wall Street Journal ● May 27, 2026
You can see the atmospheric pressure drop pretty quick before noon.
From Los Angeles Times ● Dec. 23, 2025
When the mercury was at the same level on both sides of the tube, the air in the closed end was at atmospheric pressure.
From "The Scientists" by John Gribbin
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.
