Synonyms for Pentecost (same or very similar meaning)
WordNet sense 1 (seventh Sunday after Easter; commemorates the emanation of the Holy Spirit to the apostles; a quarter day in Scotland):
WhitsundayWordNet sense 2 ((Judaism) Jewish holy day celebrated on the sixth of Sivan to celebrate Moses receiving the Ten Commandments):
Shabuoth, Shavous, Shavuot, Shavuoth, Feast of WeeksFrom the ODE community, based on WordNetadd/edit