Let's say: You're very good at computer stuff, such as programming, fixing hardware, etc. When it comes to things like that, you're one of the best, if not the best! And one day, a friend comes over to your house, using your computer and talking non-stop about why you should use these software instead and not those ones installed in your computer... things like that, even though you have much better knowledge in this field than him. I mean your friend is trying hard to show-off his skills without having known that the person he's talking to (it's you) is miles better than him.

So which phrase should describe this situation the best?

Edit: To be a little more specific, I am looking for a phrase (if it really exists of course) to describe the friend's action, so it can be used for the expert in that situation to say or another friend/third-party which happens to have listened/seen the conversation/action. For instance:


Your friend named A (less knowledge than you): "Man, you should've installed Windows 10 like I said than this useless Linux distro, and believe me when I say that, it can't even install some common software like foobar."

You: (Sigh...)

Your friend named B: "Lol, A, please just stop, don't try to make fun of yourself here, he knows much better than you when it comes to things like that."

So what I want here is a phrase than can be replaced with this line: "don't try to make fun of yourself here, he knows much better than you when it comes to things like that."

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    Phrase to describe the friend's action or the phrase to describe the position of the person who is an expert? Commented Mar 22, 2016 at 6:03
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    teaching grandma to suck eggs See Phrase Finder: phrases.org.uk/meanings/118200.html Any user is free to use this answer. I haven't the time to post it myself.
    – Mari-Lou A
    Commented Mar 22, 2016 at 8:24
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    @johnchae Like "Ah! Says the expert!" in a sarcastic way? Commented Mar 22, 2016 at 10:10
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    @johnchae I think I responded for the same comment. I am not sure of such a response. Please check my comment and if you are looking for a mocking response of similar kind, let me know. Commented Mar 22, 2016 at 10:22
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    I'm not sure if there's an idiom which fits the situation which you have described. But if it were me, I would tell the amateur magician that I am a magician by profession and then criticize or praise his work. And if the amateur believes he knows more than me, when he clearly doesn't, then I would brush him off with the same phrase. The simpler "Don't teach a fish to swim" would also work, but it is not an "English" idiom, it's Latin in origin en.wikipedia.org/wiki/Teach_fish_how_to_swim
    – Mari-Lou A
    Commented Mar 22, 2016 at 16:44

2 Answers 2


This is known as teaching your Grandmother to suck eggs.

A phrase that indicates you are telling someone how to do something that they have done with great skill for years. The idiom dates back centuries, being used in Henry Fielding's Tom Jones, published in 1749.

  • Thank you, your answer is much appreciated. Though I want something more and would be applied in "doing an action", not just "giving advice". For example: (let me copy-paste from my comment above) "You are a professional magician and there's an amateur who has been trying to surprise you/show-off his skills in front of you (he doesn't know you're a true magician)/" So which phrase would apply for this situation?"
    – johnchae
    Commented Mar 22, 2016 at 15:59

Probably not the exact answer, however I think it could be true in some similar situations:

Carry coals to Newcastle:

To carry Coals to Newcastle, that is to do what was done before; or to busy one's self in a needless employment.

  • Thank you but yes, it's not quite the answer I'm looking for. But thank you so much for taking the time for me!
    – johnchae
    Commented Mar 22, 2016 at 10:11

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