Whitsunday

noun2

1. •
   The Sunday on which the feast or festival of Pentecost falls, seven weeks after Easter.

   • 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. — 1773
2. •
   (Scotland) A quarter day falling on 15th May.