From Longman Dictionary of Contemporary Englishgo in (at) one ear and out (at) the othergo in (at) one ear and out (at) the otherinformalFORGET if information goes in one ear and out the other, you forget it as soon as you have heard it I don’t know why I tell her anything. It just goes in one ear and out the other. → ear
Examples from the Corpus
go in (at) one ear and out (at) the other• It goes in one ear and out the other. 