The headache, numbness, and discomfort that is experienced by a person when a power nap turned into a 4-hour nap marathon. It's when a 30-minute nap turns into a 4-hour nap that is not quite long enough to qualify for a true sleeping session.
It's 7PM on a Friday night. You decide to take a 30 minute nap, so that you'll have more energy for the weekend's events. 4 hours later, the intended 30 minute power nap turned into a 4-hour nap marathon.
Eddie: What time is?
Jane: It's 11PM
Eddie: Oh man! I was supposed to wake up before 8PM to meet up with the guys, but now I have this crazy headache.
Jane: You are experiencing a naphangover.