Entry 2 senses · 2 variants Webster, 1913 Semidouble · Sem·i·dou·ble · IPA n. a. 01 n. An office or feast celebrated with less solemnity than the double ones. See Double, n., 8. 1. An office or feast celebrated with less solemnity than the double ones. See Double, n., 8.(Eccl.) See: Double 02 a. Having the outermost stamens converted into petals, while the inner ones remain perfect; -- said of a flower. 1. Having the outermost stamens converted into petals, while the inner ones remain perfect; -- said of a flower.(Bot.)