/ Dictionary / Index I isotretinoin: Meaning and Definition of Find definitions for: i•so•tre•tin•o•in Pronunciation: (ī"sō-tri-tin'ō-in, -oin), [key] — n. Pharm. a yellowish-orange to orange crystalline powder, CHO, used in the treatment of cystic acne. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. isotopy isotropic Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language