[lee-thuh l]
  1. of, relating to, or causing death; deadly; fatal: a lethal weapon; a lethal dose.
  2. made or carried out to cause death: a lethal chamber; a lethal attack.
  3. causing great harm or destruction: The disclosures were lethal to his candidacy.

Origin of lethal

1575–85; < Latin lētālis, equivalent to lēt(um) death + -ālis -al1; spelling (hence pronunciation) with -h- by association with Greek lḗthē oblivion
Related formsle·thal·i·ty, le·thal·ness, nounle·thal·ly, adverbhy·per·le·thal, adjectivenon·le·thal, adjectivenon·le·thal·ly, adverbsem·i·le·thal, adjective

Synonyms for lethal

1. See fatal.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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Contemporary Examples of non-lethal

Historical Examples of non-lethal

British Dictionary definitions for non-lethal


  1. able to cause or causing death
  2. of or suggestive of death
Derived Formslethality (liːˈθælɪtɪ), nounlethally, adverb

Word Origin for lethal

C16: from Latin lēthālis, from lētum death
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for non-lethal



1580s, from Late Latin lethalis, alteration of Latin letalis "deadly, fatal," from letum "death," of uncertain origin. Form altered in Late Latin by association with lethe hydor "water of oblivion" in Hades in Greek mythology, from Greek lethe "forgetfulness."

Online Etymology Dictionary, © 2010 Douglas Harper

non-lethal in Medicine


  1. Capable of causing death.
  2. Of, relating to, or causing death.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.