To keep sleeping while something loud or important happens, so you miss it: sleep through the alarm, sleep through the storm, sleep through the whole class. The thing you missed comes right after "through" and must be there. Parents also use a special version: a baby "sleeps through the night" — sleeps until morning without waking, which is good news, not missing anything.

（吵鬧、事情發生時）照睡不醒、一覺睡過去