1
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Phrase(s): Look who’s talking!
Fig. You are guilty of doing the same thing that you have criticized someone else for doing or that you accused someone else of doing. • Andy: You criticize me for being late! Look who’s talking! You just missed your flight! Jane: Well, nobody’s perfect. • Mary: You just talk and talk, you go on much too long about practically nothing, and you never give a chance for anyone else to talk, and you just don’t know when to stop! Sally: Look who’s talking!
McGrawhill's American Idioms And Phrasal Verbs
2
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You're in no position to criticize, as in I wish Kate would be on time for once.? You do? Look who's talking! This colloquial idiom dates from the mid-1900s, although another version, you can't talk, is a century or so older.
American Heritage Idioms