Whit"sun*day (?), 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.
See the Note under Term, n., 12.
© Webster 1913.