lighten something up
phrasal verb with lighten verb uk/ˈlaɪ.tən/ us/ˈlaɪ.t̬ən/
使…轻松活泼，使…不那么严肃
to make a speech or piece of writing less serious
I thought I'd slip in a few jokes to lighten up the talk. 我本想在讲话中加几个笑话来调剂一下气氛。
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