noun
masquerade ball; masked ball
A formal dance event where participants wear masks and often costumes.
今夜の仮面舞踏会には、華やかな衣装で参加する予定です。
I plan to attend tonight's masquerade ball in a gorgeous costume.
Compound of 仮面 (kamen, 'mask') + 舞踏会 (butōkai, 'ball, dance party').