a Jewish holiday, the Feast of Weeks, or Pentecost, originally celebrating the spring harvest, now chiefly commemorating the revelation of the Law at Mount Sinai: celebrated on the 6th & 7th days of Sivan
Word origin
< Heb (chag-ha) shavuot, (the Feast of) Weeks < shavua, week < sheva, seven; akin to IE *septṃ, seven