also: うちあげパーティ
noun
wrap party; completion celebration
A party held after a project, performance run, or event to celebrate its successful completion. Often used for theater, film, concerts, or corporate projects.
See also: 打ち上げ会
舞台の千秋楽の後、打ち上げパーティーが開かれた。
After the final performance, a wrap party was held.
プロジェクトが無事に終わったので、今夜は打ち上げパーティーだ。
Since the project finished successfully, tonight is the celebration party.
打ち上げ会 is a more general term for a completion celebration or wrap meeting, while 打ち上げパーティー specifically implies a party atmosphere.
Compound of 打ち上げ (completion, launch) and パーティー (party). The term 打ち上げ originally refers to 'launching' or 'finishing up' a project, and here it is combined with the loanword パーティー to describe a celebratory gathering.