直譯是 display one's slight skill before an expert. (在行家面前顯示身手)
意譯有(老外常這樣表達):
1.teach a fish to swim
2.teach one's grandmother to suck eggs
請看下列例句:
He is always tell the director how to run the business; that's like teach his grandmother to suck eggs
他老是對總裁說該如何管理業務,就跟班門弄斧似的
Never offer to teach fish to swim.
不要教魚遊泳; 不要班門弄斧。