/ Dictionary / Index S semicircle: Meaning and Definition of Find definitions for: sem•i•cir•cle Pronunciation: (sem'i-sûr"kul), [key] — n. Also calledhalf of a circle; the arc from one end of a diameter to the other. anything having or arranged in the form of a half of a circle. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: semicircle (Thesaurus) semicentennial semicircular canal Related Content Daily Word Quiz: cetacean Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language