teach your grandmother to suck eggs
US /tiːtʃ jʊər ˈɡrændˌmʌðər tə sʌk ɛɡz/
UK /tiːtʃ jʊər ˈɡrændˌmʌðər tə sʌk ɛɡz/
1.
班门弄斧, 教导比自己更有经验的人
to try to teach someone something they already know, especially someone who is more experienced than you
:
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I tried to explain how to use the new software to my boss, but it was like teaching my grandmother to suck eggs; she's been using similar programs for decades.
我试图向老板解释如何使用新软件，但这就像班门弄斧；她使用类似的程序已经几十年了。
•
He started giving me advice on cooking, but I've been a chef for twenty years. It was definitely a case of teaching your grandmother to suck eggs.
他开始给我烹饪建议，但我已经做了二十年厨师了。这绝对是班门弄斧。