/ Dictionary / Index S sesquicentennial: Meaning and Definition of Find definitions for: ses•qui•cen•ten•ni•al Pronunciation: (ses"kwi-sen-ten'ē-ul), [key] — adj. pertaining to or marking the completion of a period of 150 years. —n. a 150th anniversary or its celebration. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: sesquicentennial (Thesaurus) sesquicarbonate sesquioxide Related Content Daily Word Quiz: stringent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language