noun
caucus; party members' meeting
A meeting of members of a political party, often to select candidates or decide policy. Used in political contexts.
党員集会で次の候補者を選ぶ。
They choose the next candidate at the party caucus.
党大会 is a larger, formal party convention, while 党員集会 is a smaller, more focused meeting of party members.
Compound of 党員 (party member) and 集会 (meeting, assembly).