a red rag to a bull
 a red rag to a bull — see red, 1
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 Main Entry: bull
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 a red rag to a bull — see red, 1
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 Main Entry: rag
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 a red rag to a bull
   Brit    informal   : something that makes a person very angry
   Just mentioning his poor marks to him was waving a red rag to a bull.
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 Main Entry: red