1. red flag - Noun
2. red flag - Phrase
something that irritates or demands immediate action
the emblem of socialist revolution
a flag that serves as a warning signal
Source: WordNetRed flag of the eating disorder: the muffin. Keep your eye on the ladies with the muffins... and sometimes I'll just eat the muffin top. Janeane Garofalo
Using a metaphor in front of a man as unimaginative as Ridcully was like a red flag to a bull, was like putting something very annoying in front of someone who was annoyed by it. Terry Pratchett
Our people will never keep the Red Flag flying here. There is only one banner that Britain flies, the one that has kept flying for centuries-the red, white and blue. Margaret Thatcher
London doesn't love the latent or the lurking, has neither time, nor taste, nor sense for anything less discernible than the red flag in front of the steam-roller. It wants cash over the counter and letters ten feet high. Henry James
I remember in 1968 when we were in Cannes, in the festival, and we were supposed to be there 10 days, and the second day the festival collapsed because the French, you know, film-makers raised the red flag in the festival and ended the festival. Miloš Forman
I learned this a long time ago. If you call a guy into your office and shut the door, if there's media around, it sends up a red flag. I never wanted to embarrass a player. Jim Leyland