/ ˈliːθl; NAmE / adjective
1.
causing or able to cause death
SYN deadly , fatal :
a lethal dose of poison
a lethal weapon
( figurative )
The closure of the factory dealt a lethal blow to the town.
2.
( informal ) causing or able to cause a lot of harm or damage :
You and that car—it's a lethal combination!
► le·thal·ly / ˈliːθəli; NAmE / adverb
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WORD ORIGIN
late 16th cent. (in the sense causing spiritual death ): from Latin lethalis , from lethum , a variant (influenced by Greek lēthē forgetfulness), of letum death.