To 'ragequit' is to abruptly quit a video game (or a job, or any frustrating activity) in anger, often noisily and without finishing what you were doing. Originally gaming slang from the 2000s, now broadly used. If your teen says they ragequit a game, they were frustrated and stopped suddenly. Harmless venting; only worth attention if quitting in anger becomes a pattern that disrupts relationships or commitments.