Computing term for a binary indicator or status marker.
In this program, processing stops when an error flag is set.
foreshadowing; sign of things to come
Colloquial use, often in discussions of stories, games, or real-life situations, referring to an event or line that hints at a future development.
That line is a death flag, isn't it.
Him suddenly becoming kind might be a sign of something.
The program sets an error flag so that processing can branch later.
The protagonist who said “I’ll definitely make it back alive” ended up fulfilling that ominous line, just as expected.
He deliberately made a weak-sounding comment to try to break the ominous flag.
parent intrusion flag; parent alert
edge flag
sign flag
idle flag
debug flag
flag sequence
From English 'flag'. The computing sense is a direct borrowing; the colloquial foreshadowing sense developed in Japanese from the idea of a flag as a marker or signal.