/ Dictionary / Index C closed set: Meaning and Definition of Find definitions for: closed' set' Pronunciation: [key] — Math. Math. a set that contains all of its accumulation points, as the set of points on and within a circle; a set having an open set as its complement. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. closed season closed shelf Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language