/ Dictionary / Index R roche alum: Meaning and Definition of Find definitions for: roche' al'um Pronunciation: (rōch), [key] an alumlike substance derived from alunite. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Rochdale Roche limit Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language