Stands for Dick Around Nap. It is when you take a nap on the couch, with the lights on, T.V. on, etc... Instead of going to your room and taking a real nap in your bed.
I walked into my house during the day and saw my brother laying on the couch with the T.V. on, so I asked him what he was doing. He replied "I am taking a NAP". I replied with " Why are you dicking around? Why don't you turn the TV off, go to your room, turn the lights off, get into bed, and take a REAL nap....instead of a fucking D.A.N.