In the United States and Canada, a prom, short for promenade, is a formal (black tie) dance, or gathering of high school students. It is typically held at the end of junior and/or senior year. It figures greatly in popular culture and is a major event among high school students. High school juniors attending the prom may call it Junior Prom while high school seniors may call it Senior Prom. In practice this may be a combined junior/senior dance.
The British synonym for the North American event would be Leavers' Ball, Leavers' Dinner, Formal or, informally, Leavers' Do. This is closer to the Australian description, although in the UK, some schools have called the above events proms. In Canada, Ireland, and Australia the termsGrad or Formal are most commonly used and the event is usually held for those graduating high school or middle school. In Ireland, the event is also known as the Debs, which is derived from Debutante.