/ Dictionary / Index C coset: Meaning and Definition of Find definitions for: co•set Pronunciation: (kō'set), [key] — n. Math. a subset of a group, formed by the consistent operation of a given element of the group on the left or right of all the elements of a subgroup of the group. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Cosenza Cosgrave Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language