semicirclePronunciation: /ˈsɛmisɜːkl/Translate semicircle | into French | into German | into Italian | into Spanish Definition of semicircle noun a half of a circle or of its circumference. a set of objects arranged in a semicircle:chairs were in a semicircle round the hearthOrigin: early 16th century: from Latin semicirculus (see semi-, circle)semicircle in other Oxford dictionaries Definition of semicircle in the US English dictionary