/ Dictionary / Index R retinoblastoma: Meaning and Definition of Find definitions for: ret•ino•blas•to•ma Pronunciation: (ret"nō-bla-stō'mu), [key] — pl. -mas, -ma•ta an inheritable tumor of the eye. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: retinoblastoma (Thesaurus) retinitis pigmentosa retinoid Related Content Daily Word Quiz: placid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language