/ Dictionary / Index O oogonium: Meaning and Definition of Find definitions for: o•o•go•ni•um Pronunciation: (ō"u-gō'nē-um), [key] — pl. -ni•a -ni•ums. one of the undifferentiated germ cells giving rise to oocytes. the one-celled female reproductive organ in certain thallophytes, usually a more or less spherical sac containing one or more eggs. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. oogenesis ooh Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language