A warning sign
He told me that he had 5 GFs in the last 2 years, which was a major red flag.
|Diva||A self-important, demanding person|
|Insta-lurking||Looking through a person's Instagram pictures|
|Facestalking||Looking through someone's pictures on Facebook|
|Green flag||A sign of approval|
A red flag is a sign that indicates you should be wary or cautious of someone or something. It may be used to warn about concerning traits in people, houses, vehicles, plans, jobs, games, etc.
The term comes from the use of actual red-colored flags to warn people of danger, whether it be on a racetrack when a crash occurs or a beach with strong rip tides. Red flag is often used in regards to relationships when determining if potential partners are worth investing in or if they have too many "deficiencies."