/ Dictionary / Index S semicentennial: Meaning and Definition of Find definitions for: sem•i•cen•ten•ni•al Pronunciation: (sem"ē-sen-ten'ē-ul, sem"ī-), [key] — adj. of or pertaining to a fiftieth anniversary. —n. a fiftieth anniversary. the celebration of this anniversary. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: semicentennial (Thesaurus) semicentenary semicircle Related Content Daily Word Quiz: neologism Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language