raise a red flag

raise a red flag

To offer a sign or signal indicating potential, incipient, or imminent danger or trouble. Didn't the fact that your accountant used to be a drug dealer raise a red flag or two when you started doing business with him? Well, it definitely raised a red flag when he got so angry at me over such a minor thing, but I never thought he could be so unreasonable to live with!

See also: flag, raise, red

Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.