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 deadliest

Contemporary Examples of deadliest

Historical Examples of deadliest

  • After all, I was her only boy, and it was to war in its deadliest form that I was going.

    In the Valley

    Harold Frederic

  • In an Italian town he is always at work, and always thumping in the deadliest manner.

  • Look at the tastes and habits of our age—the deadliest enemies of true religion!

    The Christian

    Hall Caine

  • If the cloud were no bigger than a man's hand, it was charged with deadliest lightning.

    Gerald Fitzgerald

    Charles James Lever

  • Could settle the deadliest quarrel in the country by crooking his little finger.

    Lord Jim

    Joseph Conrad

British Dictionary definitions for deadliest


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 deadliest



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