/ Dictionary / Index O opportunistic: Meaning and Definition of Find definitions for: op•por•tun•is•tic Pronunciation: (op"ur-t-nis'tik, -ty-), [key] — adj. adhering to a policy of opportunism; practicing opportunism. Pneumocystis pneumonia is an opportunistic disease that often strikes victims of AIDS. (of a microorganism) causing disease only under certain conditions, as when a person's immune system is impaired. (of a disease or infection) caused by such an organism:Pneumocystis pneumonia is an opportunistic disease that often strikes victims of AIDS. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: opportunistic (Thesaurus) opportunism opportunity Related Content Daily Word Quiz: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language