/ Dictionary / Index O oocyst: Meaning and Definition of Find definitions for: o•o•cyst Pronunciation: (ō'u-sist"), [key] — n. Biol. the encysted zygotic stage in the life cycle of some sporozoans. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ooblast oocyte Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language