1. of or causing death; deadly; fatal: a lethal weapon; a lethal dose. 2. made to cause death: a lethal injection. 3. causing great harm; disastrous: The disclosures were lethal to his candidacy. Learn what lethal means with clear definitions, pronunciation, synonyms, and real-world examples. Simple explanations to help you use lethal correctly. 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. / ˈli·θəl / able to cause or causing death; extremely dangerous: a lethal weapon (Definition of lethal from the Cambridge Academic Content Dictionary © Cambridge University Press) / ˈli·θəl / able to cause or causing death; extremely dangerous: a lethal weapon (Definition of lethal from the Cambridge Academic Content Dictionary © Cambridge University Press) Wishlist the full version of Lethal on Steam! Win in 1 turn. Can you find lethal? Can you beat this puzzle in 1 turn? lethal applies to something that is bound to cause death or exists for the destruction of life. Experience nature, scanning any creature you find to add them to your bestiary. Explore the wondrous outdoors and rummage through their derelict, steel and concrete underbellies. LETHAL definition: of, relating to, or causing death; deadly; fatal: a lethal dose. See examples of lethal used in a sentence. Some common synonyms of lethal are deadly, fatal, and mortal. While all these words mean causing or capable of causing death, lethal applies to something that is bound to cause death or exists for the destruction of life.