red rag

• (something to enrage): Shortened from red rag to a bull.

red rag (plural red rags)

1. Something that will enrage another particular person.
   • 2008, Sep 24, by Lindesay Irvine in guardian.co.uk, Collins, we're lost for words: let's call your bluff,

     Collins dictionaries has announced that the inclusion of 2,000 new words in its forthcoming new edition means that some of the dustier corners of its lexicon will have to be swept into the semantic dustbin. Farewell embranglement, recrement, fusby and numerous others. This will be a red rag to books bloggers everywhere.

2. (obsolete, slang, derogatory) A person's tongue.
   • 1869, William Combe; Thomas Rolandson, The Three Tours of Doctor Syntax, page 194:

     For well I know by your glib tongue, / To what fine country you belong, / And if your red rag did not shew it, / By your queer fancies I should know it.

• (tongue): 1873, John Camden Hotten, The Slang Dictionary

• Drager, Gerard, Grader, grader, regard