show off before an expert/teach a fish how to swim

班門弄斧

Lu Ban (魯班) was supposed to be a consummate carpenter in ancient times.

古代有一個(gè)建筑和雕刻技術(shù)非常高超的人，名叫魯班。

It is said that he once carved a wooden phoenix that was so lifelike that it actually flew in the sky for three days.

傳說他曾用木頭制作了一只五彩斑斕的鳳凰，能夠在空中飛翔三天不掉下來。

Thus it was considered the height of folly to show off one‘s skill with an axe in front of Lu Ban.

誰敢在魯班門前賣弄使用斧子的技術(shù)，也就是說，想在大行家面前顯示自的本領(lǐng)，這種太不謙虛的可笑行為，就叫做“班門弄斧”( 這句成語有時(shí)也用作自謙之詞，表示自己不敢在行家面前賣弄自己的小本領(lǐng))。

【成語活用】

I’m making a fool of myself trying to show off before an expert like you.

在你面前班門弄斧，太不好意思了。

“班門弄斧”的英文表達(dá)，常用“to teach a fish how to swim”，也就是說“去教一條魚怎么游泳”，魚本來就會游泳，怎么還用人來教呢?所以英語中要表示一個(gè)人“班門弄斧”做無用的行為的時(shí)候，就會用“to teach a fish how to swim”。舉例來說：

My son， fresh out of college， keeps telling me how to run my business. But I‘ve been making good money for 30 years so he’s teaching a fish how to swim.

我的兒子大學(xué)剛畢業(yè)，可是他卻不斷地來告訴我應(yīng)該怎麼做生意.我叁十年來生意做得很好，賺了不少錢.所以，他來告訴我怎麼做生意簡直是班門弄斧。