The hangover-like feeling one experiences when waking up from a mid-day nap. (Most likely won't experience nap hangover if nap does not exceed 30 minutes).
"Yo that naphangover is really messin you up, you shouldnt'a taken that nap"
The fuzzy, drowsy, and nauseous feeling that follows a long napping period, usually lasting 15-30 minutes.
Kyle: Why does Danny seem so tiresome?
Joe: He's still recuperating from his nap hangover, Mr. Patterson's lecture on electromagnetism put him to sleep.
When you are trying to power nap but instead end up over-sleeping and you wake up more tired than you were before. You have a nap hangover. Symptoms include: drowsiness, headaches, yawning, feeling fuzzy, and pressing the snooze button too many times.
Me: bro, I meant to take a 20 min power nap and ended up sleeping for 2 hours instead. My head is hella fuzzy.
Friend: sounds like you have a nap hangover. Better get some coffee to wake you up.
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.