[in.troit] n [ME, fr. MF introite, fr. ML introitus, fr. L, entrance, fr. introire to go in, fr. intro- + ire to go--more at issue] (15c) 1 often cap: the first part of the traditional proper of the Mass consisting of an antiphon, verse from a psalm, and the Gloria Patri
2: a piece of music sung or played at the beginning of a worship service