noun
extraordinary party convention
A special or emergency convention of a political party, held outside the regular schedule.
党首の辞任を受けて、臨時党大会が開かれた。
Following the resignation of the party leader, an extraordinary party convention was held.
Refers to a regular party convention, while 臨時党大会 is an extraordinary one called for a specific urgent matter.
Compound of 臨時 (extraordinary, special) + 党 (party) + 大会 (convention, general meeting).