noun
parent intrusion flag; parent alert
Internet slang used by streamers to signal that a parent has entered the room, often prompting a change in behavior or topic.
配信中に親フラグが立ったので、急に敬語になった。
A parent flag went up during the stream, so I suddenly switched to polite speech.
「親フラグ注意」とチャットに流れた
A warning about a parent flag appeared in the chat.