[Trin.i.ty] n [ME trinite, fr. OF trinite, fr. LL trinitat-, trinitas state of being threefold, fr. L trinus threefold] (13c) 1: the unity of Father, Son, and Holy Spirit as three persons in one Godhead according to Christian dogma
2. not cap: a group of three closely related persons or things
3: the Sunday after Whitsunday observed as a feast in honor of the Trinity