whitsunday, n. [White + Sunday.].
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. [1913 Webster]
See the Note under Term
, 12. [1913 Webster