/ Dictionary / Index O oidium: Meaning and Definition of Find definitions for: o•id•i•um Pronunciation: (ō-id'ē-um), [key] — pl. o•id•i•a one of the conidia that are borne in chains by certain fungi. (in certain fungi) a thin-walled spore derived from the fragmentation of a hypha into its component cells. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. -oidea oik Related Content Daily Word Quiz: nonchalant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language