/ Dictionary / Index O opisthobranch: Meaning and Definition of Find definitions for: o•pis•tho•branch Pronunciation: (u-pis'thu-brangk"), [key] — n. any gastropod mollusk of the order Opisthobranchia, as the sea slugs, sea butterflies, and sea hares, characterized by a vestigial or absent mantle and shell and two pairs of tentacles. —adj. of or pertaining to the opisthobranches. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. opistho- opisthodomos Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language