lethal
Americanadjective
-
able to cause or causing death
-
of or suggestive of death
Synonym Usage
See fatal.
Other Word Forms
Etymology
Origin of lethal
First recorded in 1575–85; from Latin lētālis, equivalent to lēt(um) “death” + -ālis -al 1; spelling (hence pronunciation) with -h- by association with Greek lḗthē “oblivion”; see Lethe ( def. )
Explanation
Lethal refers to anything dangerous enough to cause death. The cobra's venom is so lethal that if you get bitten and can't find the antidote, it's lights out forever. Poisonous spiders, guns, knives, and radiation — all of these things can be lethal because they have the ability to kill. Even some substances that on their own aren't dangerous can become lethal in large quantities. Eating a peanut butter sandwich won't hurt most people, but it can be lethal to those with a nut allergy. Words like deadly and fatal have meanings that are similar to lethal.
Vocabulary lists containing lethal
100 SAT Words Beginning with "J," "K," and "L"
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A Long Way Gone
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Silent Spring
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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.
"Guaranteeing our naval and joint forces have the lethal firepower they need to deter aggression and protect the homeland is paramount," Cao said in a statement.
From Barron's ● Aug. 17, 2026
“Together, there could be a possibility they’re quite lethal. And separately it looks like they are not at all lethal, but just very effective.”
From Los Angeles Times ● Aug. 15, 2026
KAMPALA, Uganda—The scariest thing about the Ebola strain ripping through East Africa this year might be rather surprising: It isn’t quite as lethal as those in earlier outbreaks.
From The Wall Street Journal ● Aug. 6, 2026
The findings suggest that glyphosate could disturb the neurochemical balance that supports normal behavior, even when the exposure is not lethal.
From Science Daily ● Aug. 6, 2026
Since mutations are random nucleotide changes, most of them are harmful or lethal, coding into existence nonfunctional enzymes.
From "Cosmos" by Carl Sagan
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.
