①If you describe someone as frivolous, you mean they behave in a silly or light-hearted way, rather than being serious and sensible.【adj.轻浮的;轻佻的;草率的】
②If you describe an activity as frivolous, you disapprove of it because it is not useful and wastes time or money.【adj.无聊的;无用的;浪费的】
①Isabelle was a frivolous little fool, vain and flighty.
②The group says it wants politicians to stop wasting public money on what it believes are frivolous
《经济学人》一篇关于极限挑战的文章 Last of the daredevils 也出现了这个表达：
[scode type="blue"]break a leg
used for wishing someone good luck.
Thanks, Penny. Oh-break a leg. Break a leg.
"Break a leg" is an idiom in theatre used to wish a performer "good luck". Well-wishers typically say "Break a leg" to actors and musicians before they go on stage to perform. The origin of the phrase remains obscure.
The expression reflects a theatrical superstition in which wishing a person "good luck" is considered bad luck. The expression is sometimes used outside the theatre as superstitions and customs travel through other professions and then into common use. Among professional dancers, the traditional saying is not "break a leg," but "merde".