[poi-zuh-nuh s]


full of or containing poison: poisonous air; a poisonous substance.
harmful; destructive: poisonous to animals; poisonous rumors.
deeply malicious; malevolent: poisonous efforts.

Origin of poisonous

First recorded in 1565–75; poison + -ous
Related formspoi·son·ous·ly, adverbpoi·son·ous·ness, nounnon·poi·son·ous, adjectivenon·poi·son·ous·ly, adverbnon·poi·son·ous·ness, nounsem·i·poi·son·ous, adjectivesem·i·poi·son·ous·ly, adverbun·poi·son·ous, adjectiveun·poi·son·ous·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for poisonous

Contemporary Examples of poisonous

Historical Examples of poisonous

  • If there is a poisonous one among them, the onion will turn black.

  • It is some of the rivers flowing into it that are poisonous.

    Aino Folk-Tales

    Basil Hall Chamberlain

  • Chemistry cannot tell us why some food is wholesome and other food is poisonous.


    James Anthony Froude

  • From this I quote the following, which is by no means the most erring and most poisonous of their shafts.

    The Book of Khalid

    Ameen Rihani

  • "They're just weeds and some of them might be poisonous," he declared.


    Emile Zola

British Dictionary definitions for poisonous



having the effects or qualities of a poison
capable of killing or inflicting injury; venomous
corruptive or malicious
Derived Formspoisonously, adverbpoisonousness, 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 poisonous

1570s, from poison (n.) + -ous. Failed 16c. rivals were poisonsome, poisonful, poisony. Earlier poisoned was used (late 15c.). Related: Poisonously; poisonousness.

Online Etymology Dictionary, © 2010 Douglas Harper

poisonous in Medicine




Relating to or caused by a poison.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.