From Longman Dictionary of Contemporary Englishsay whensay whenASK FOR something/ASK somebody TO DO somethingused to ask someone to tell you when to stop pouring them a drink or serving them food because they have got enough → say
Examples from the Corpus
say when• For what could he say when asked where he lived or why he never invited his friends to his house?• So the Knight says when he cuts the tale short.• He had quit, he said, because he no longer knew what to say when head teachers complained about bureaucratic interference.• What will Gurder say when I tell him?• She said when she saw you last you were as thin as a rake - and she's right.• Underneath it says when she was born.• There are some things you just can not say when the person is present.• They say when you go on to the Stock Market you should be worried because you can lose your strength. 