noun
Computing term for a binary indicator or status marker.
このプログラムではエラーフラグが立つと処理が止まる。
In this program, processing stops when an error flag is set.
noun
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.
あのセリフは死亡フラグだよね。
That line is a death flag, isn't it.
彼が急に優しくなったのは、何かフラグかもしれない。
Him suddenly becoming kind might be a sign of something.