/ Dictionary / Index O ommatidium: Meaning and Definition of Find definitions for: om•ma•tid•i•um Pronunciation: (om"u-tid'ē-um), [key] — pl. -tid•i•a one of the radial elements composing a compound eye. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ommatidium (Thesaurus) ommateum ommatophore Related Content Daily Word Quiz: fabricate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language