/ Dictionary / Index G gymnodinium: Meaning and Definition of Find definitions for: gym•no•din•i•um Pronunciation: ( jim"nu-din'ē-um), [key] — pl. -din•i•a any marine or freshwater dinoflagellate of the genus Gymnodinium, certain species of which cause red tide. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. gymnocarpous gymnogynous Related Content Daily Word Quiz: supercilious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language