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

Related Words for deadliness

mortality, lethality

Examples from the Web for deadliness

Contemporary Examples of deadliness

Historical Examples of deadliness

  • There was the deadliness of the story: its lack of malice, even of resentment.

    Alice Adams

    Booth Tarkington

  • Silently and with deadliness apparent in every move they approached him.

    In the Orbit of Saturn

    Roman Frederick Starzl

  • Slander nips it like a frost; in deadliness it is second only to ridicule.

    Mistress Wilding

    Rafael Sabatini

  • But the knowledge of his deadliness kept him from being made a target.

    When the West Was Young

    Frederick R. Bechdolt

  • As to Navel-ill, much has been written on the deadliness of the complaint.

British Dictionary definitions for deadliness


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 deadliness



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