(n.) The seventh Sunday, and the fiftieth day, after Easter; a festival of the church in commemoration of the descent of the Holy Spirit on the day of Pentecost; Pentecost; -- so called, it is said, because, in the primitive church, those who had been newly baptized appeared at church between Easter and Pentecost in white garments.
WHITSUNDAY
Meaning of WHITSUNDAY in English
Webster's English dictionary. Английский словарь Webster. 2012