[ lee-thuh l ]
/ ˈli θəl /


of, relating to, or causing death; deadly; fatal: a lethal weapon; a lethal dose.
made or carried out to cause death: a lethal chamber; a lethal attack.
causing great harm or destruction: The disclosures were lethal to his candidacy.

Nearby words

  1. leta,
  2. letch,
  3. letchworth,
  4. letdown,
  5. letha,
  6. lethal chamber,
  7. lethal dose,
  8. lethal factor,
  9. lethal gene,
  10. lethal midline granuloma

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

1. See fatal.

Related forms
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for lethally

British Dictionary definitions for lethally


/ (ˈliːθəl) /


able to cause or causing death
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 lethally



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

Medicine definitions for lethally


[ lēthəl ]


Capable of causing death.
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.