A nap that is at least 15 minutes long, but not greater than 1 hour.
(Unless, you tell your friends that you are going to take a powernap at 2:00 am and end up waking back up again at 7:00 the next morning)
A code word said for Masturbation in a situation where actually saying Masturbation would be inappropriate or dirty. As in if someone knocks on the door you say "I'm taking a powernap"
When you're supposed to sleep for 20 minutes and end up sleeping for 2 hours or more. In stead of feeling refreshed, you feel completely tapped of energy and you have the breath of a horse six days dead.
I was going to take a powernap this afternoon, but when I woke up 3 hours later with a awful taste in my mouth I figured I'd taken a powertap instead.