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general::
Phrase(s): Drop the subject! [and] Drop it!
Fig. Do not discuss it further! • Bill: Sally, you’re gaining a little weight. I thought you were on a diet. Sally: That’s enough! Drop the subject! • Bill: That house is a mess. I wonder who lives there. Mary: That’s my aunt’s house. Just what did you want to know about it? Bill: Oh, drop it! Sorry I asked.
McGrawhill's American Idioms And Phrasal Verbs