/ Dictionary / Index C Colosseum: Meaning and Definition of Find definitions for: Col•os•se•um Pronunciation: (kol"u-sē'um), [key] — n. an ancient amphitheater in Rome, begun a.d. c70 by Vespasian, having the form of an oval 617 by 512 ft. (188 by 156 m). (l.c.) coliseum. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: colosseum (Thesaurus) colossal Colossian Related Content Daily Word Quiz: lunar Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language