behaviour that is silly and not serious, or things that are silly and not important愚蠢轻率所为;无关痛痒的事物
You shouldn't treat such a serious subject with frivolity.对待如此严肃的话题不能敷衍轻视。
I'm far too busy to waste time on frivolities like going to the cinema.我忙得不可开交,不会把时间浪费在看电影之类无聊的事上。