[Pen.te.cost] n [ME, fr. OE pentecosten, fr. LL pentecoste, fr. Gk pentekoste, lit., fiftieth day, fr. pentekostos fiftieth, fr. pentekonta fifty, fr. penta- + -konta (akin to L viginti twenty)--more at vigesimal] (bef. 12c) 1: shabuoth
2: a Christian feast on the seventh Sunday after Easter commemorating the descent of the Holy Spirit on the apostles--called also Whitsunday