a. Of, pertaining to, or observed at, Whitsuntide; as, Whitsun week; Whitsun Tuesday; Whitsun pastorals. [ 1913 Webster ]

n. [ White + Sunday. ] 1. (Eccl.) 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 ]

2. (Scots Law) See the Note under Term, n., 12. [ 1913 Webster ]

n. [ Whitsunday + tide. ] The week commencing with Whitsunday, esp. the first three days -- Whitsunday, Whitsun Monday, and Whitsun Tuesday; the time of Pentecost. R. of Gloucester. [ 1913 Webster ]