What is the meaning of the idiom " Slip off"?

Leave quickly without being noticed

The idiom "slip off" can mean leave quickly without being noticed. It is used to describe someone who leaves a place quietly and discreetly, often in order to avoid being seen or caught. For example, you might say "I slipped off to the bathroom during the meeting."

The other options are not correct. "Steal quietly without being caught" would be "slink off." "Sliding quickly" would be "slipping." "Sleeping in a moment" would be "dozing off."