Red Flag
red flag; a warning sign about a person or relationship (anglicism)
Origin
Anglicism, literally 'red flag'. As far back as the 19th century the red flag served as a general warning signal (for instance at beaches before dangerous currents). From around late 2021 the term spread via social media into youth slang and denotes a warning sign of problematic behaviour - especially in dating, such as jealousy or constantly speaking negatively about others.
Building blocks
Words in this expression
Examples
Er antwortet Tagen – Red Flag.
He only replies after three days — red flag.