[mass noun]extreme amusement, especially when expressed by laughter (尤指由笑声表达的)极度快乐 his incredulous expression was the cause of much hilarity. 他那怀疑的神情引人大笑。 ■boisterous merriment 欢闹,狂欢 the noisy hilarity of the streets. 街上的狂欢。
语源
late Middle English (in the sense 'cheerfulness'): from French hilarité, from Latin hilaritas 'cheerfulness, merriment', from hilaris (see hilarious)