/ Dictionary / Index R roister: Meaning and Definition of Find definitions for: roist•er Pronunciation: (roi'stur), [key] — v.i. to act in a swaggering, boisterous, or uproarious manner. to revel noisily or without restraint. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: roister (Thesaurus) roily Rojas Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language