Tell me when to stop. Typically said when one is filling a container with something. I'll pour the cereal, you say when, OK?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
Inf. Tell me when I have given you enough of something, usually a liquid. (Sometimes answered simply with When.) Tom (pouring milk into Fred's glass): Say when, Fred. Fred: When. John: Do you want some more juice? Mary: Yes. John: Okay. Say when.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
say ˈwhenused to ask somebody to tell you when you should stop pouring a drink or serving food for them because they have enough
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