Definition of Jack and Jill party in English:

Jack and Jill party

noun

US
  • 1A party attended by male and female guests (now dated).

  • 2Specifically a celebration for a couple soon to be married, to which both male and female friends are invited; compare "stag do"; "hen do".

Origin

Late 19th century; earliest use found in Daily Reflector (Norwalk, Ohio).