Noun

1. The Sunday of the feast of Pentecost, seven weeks after Easter, when traditionally many Christians would be baptised, wearing white clothes
   • 1773: John Byrom, On Whitsunday in Miscellaneous Poems - Jesus, ascended into Heav'n again/Bestow'd this won'drous Gift upon good Men/That various Nations, by his Spirit led,/All understood what Galileans said.
   • 2004: Vicki K Black, Welcome to the Church Year: An Introduction to the Seasons of the Episcopal Church - An older name for this day [Pentecost] is Whitsunday, or “white Sunday,” named for the white garments worn by the newly baptised.
2. A quarter day, falling on 15th May