When you throw a slumber party, you invite your friends to spend the night at your house. If you're invited to a slumber party, pack your sleeping bag (but you may not use it)!
Kids and teenagers are the most likely to attend slumber parties, although there's no reason adults can't also celebrate special occasions in their pajamas. At a typical slumber party, guests do things like play games, watch movies, and eat pizza before staying up late laughing and talking. You can also call a gathering like this a pajama party or a sleepover. Slumber party dates from the 1940s, from slumber, or "sleep."