[ op-er-too-nis-tik, -tyoo- ]
/ ˌɒp ər tuˈnɪs tɪk, -tyu- /


adhering to a policy of opportunism; practicing opportunism.
  1. (of a microorganism) causing disease only under certain conditions, as when a person's immune system is impaired.
  2. (of a disease or infection) caused by such an organism: Pneumocystis pneumonia is an opportunistic disease that often strikes victims of AIDS.

Nearby words

  1. opponency,
  2. opponent,
  3. opportune,
  4. opportunism,
  5. opportunist,
  6. opportunistic infection,
  7. opportunity,
  8. opportunity cost,
  9. opportunity shop,
  10. opposable

Origin of opportunistic

First recorded in 1890–95; opportunist + -ic

Related formsop·por·tun·is·ti·cal·ly, adverbun·op·por·tun·is·tic, adjective

Can be confusedopportune opportunistic

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

Examples from the Web for opportunistically

British Dictionary definitions for opportunistically


/ (ˌɒpətjʊˈnɪstɪk) /


of or characterized by opportunism
med (of an infection) caused by any microorganism that is harmless to a healthy person but debilitates a person whose immune system has been weakened by disease or drug treatment
Derived Formsopportunistically, adverb

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 opportunistically



1889, see opportunist + -ic. Related: Opportunistically.

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for opportunistically


[ ŏp′ər-tōō-nĭstĭk ]


Of or relating to an organism capable of causing disease only in a host whose resistance is lowered.
Of or relating to a disease caused by an opportunistic organism.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.