kickoff party; rally; pep party
A gathering held to boost morale and determination before a project, campaign, or competition.
新プロジェクトの決起会を開いた。
We held a kickoff party for the new project.
選挙の決起会で支持者を鼓舞した。
They rallied supporters at the election pep party.
Compound of 決起 (kekki, 'rising up with determination') and 会 (kai, 'meeting'). The exact historical derivation is uncertain.