look up any word, like snitch bitch:
 
1.
The act - either planned or unplanned - of falling to sleep after masturbating.
I was just going to rub one out, but I ended up masternapping for an hour.

Bob's been away from his wife for two days, so he went upstairs for a masternap.
by ScottNWDC May 16, 2011
 
2.
When you masturbate and the climax is forceful enough to knock one into slumber.

Invented by Jeremy from Boise.
"Dude, you look well rested."

"Ya, bro, that's because I took a master nap after school today!"
by MasterNapper September 05, 2011
 
3.
Where somebody goes and masturbates, then quickly falls asleep.
"gotta go masternap"

"*Fap Fap Fap Fap*

"Zzzzzzzzzzzzz...."
by Master Napper October 02, 2011
 
4.
When a male/female masturbates before bed, in an attempt to fall asleep during orgasm. Masturbation + Nap= Maternap
Timmy: jeez man you were out like a flash last night...?

Billy: yeah bro, had a cheeky masternap and fell right asleep

Timmy: aww man WTF thats sick

Billy: dont lie....we have all done it

Timmy: yeah....
by xXmC-KeNzIeXx November 18, 2011