adjective, dead·li·er, dead·li·est.


in a manner resembling or suggesting death: deadly pale.
excessively; completely: deadly dull.

Origin of deadly

before 900; Middle English deedli(ch), Old English dēadlīce. See dead, -ly
Related formsdead·li·ness, nounnon·dead·ly, adjective
Can be confuseddeadly deathly

Synonyms for deadly

1. See fatal. 4. dull, tedious, tiresome. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for deadlier

Contemporary Examples of deadlier

  • With a mortality rate of 70 percent, the more cases that arise, the deadlier this epidemic becomes.

    The Daily Beast logo
    The Race for the Ebola Vaccine

    Abby Haglage

    January 7, 2015

  • With dozens of shootings in a weekend, the Windy City has earned another, deadlier moniker.

    The Daily Beast logo
    How Chicago Became ‘Chiraq’

    Michael Daly

    April 22, 2014

  • The tragedy in West Virginia reminds us that some careers are deadlier than others.

    The Daily Beast logo
    The 20 Most Dangerous Jobs

    The Daily Beast

    April 8, 2010

Historical Examples of deadlier

  • But I bethought me of something else that would make a deadlier missile.

    The Strolling Saint

    Raphael Sabatini

  • No deadlier instrument was ever invented by the cruelty of man.

  • "Your touch is deadlier than you know, perhaps," says Mr. Browne, lightly.

    April's Lady

    Margaret Wolfe Hungerford

  • The Tribune raised, for a deadlier blow, the revengeful blade.


    Edward Bulwer Lytton

  • There is not a surer shot, or a deadlier foe on earth then Persimmon Bill.

British Dictionary definitions for deadlier


adjective -lier or -liest

likely to cause deathdeadly poison; deadly combat
informal extremely boring

adverb, adjective

like death in appearance or certaintydeadly pale; a deadly sleep
Derived Formsdeadliness, noun
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 deadlier



Old English deadlic "mortal, subject to death," also "causing death;" see dead + -ly (1). Meaning "having the capacity to kill" is from late 14c. (Old English words for this included deaðbærlic, deaðberende).

Online Etymology Dictionary, © 2010 Douglas Harper