lethal

UK: /ˈliːθ^əl/ US: /ˈliθəl/ ,(lē′thəl)

WordReference Random House Learner's Dictionary of American English © 2025

le•thal /ˈliθəl/   adj. 

1. of or causing death;
   deadly;
   fatal:
   a lethal weapon; a lethal injection.

le•thal•ly, adv. 

WordReference Random House Unabridged Dictionary of American English © 2025

le•thal  (lē′thəl), adj. 

1. of, pertaining to, or causing death;
   deadly;
   fatal:
   a lethal weapon; a lethal dose.
2. made to cause death:
   a lethal chamber; a lethal attack.
3. causing great harm or destruction:
   The disclosures were lethal to his candidacy.

• Latin lētālis, equivalent. to lēt(um) death + -ālis -al¹; spelling, spelled (hence pronunciation, pronounced) with -h- by association with Greek lé̄thē oblivion
• 1575–85

le•thal′i•ty, le′thal•ness, n. 
le′thal•ly, adv. 
Synonyms

• 1. See fatal. 

Collins Concise English Dictionary © HarperCollins Publishers::

lethal / ˈliːθəl/ adjective

1. able to cause or causing death
2. of or suggestive of death

Etymology: 16th Century: from Latin lēthālis, from lētum death

lethality / liːˈθælɪtɪ/ noun

ˈlethally adverb