What you get after fucking a guy in the ass when he hasn't taken a dump in a few days. A Penis covered in Poo.
Grandpa (in a pirate voice): arrrrrgggg, Billy. Me matey. Shiver me anus!
Billy: first mate reporting for duty!
Grandpa: 'tis a fine instrument you got there, Billy. All hands on the poop deck.
Billy: oh Gramps. Here it comes...
Grandpa: garrrrrrrrrrrrrrrrrrr. That's the stuff.
10 minutes later:
Billy: awwwwww - sick. Grandpa, I have a Poonis.
Grandpa: yarrrr. Gross. Time for a colostomy bag...
Billy: first mate reporting for duty!
Grandpa: 'tis a fine instrument you got there, Billy. All hands on the poop deck.
Billy: oh Gramps. Here it comes...
Grandpa: garrrrrrrrrrrrrrrrrrr. That's the stuff.
10 minutes later:
Billy: awwwwww - sick. Grandpa, I have a Poonis.
Grandpa: yarrrr. Gross. Time for a colostomy bag...
by Pollup October 3, 2008
Get the Poonismug. by Bman December 9, 2002
Get the Poonismug. Its original meaning was a peice of poo in the shape of a penis. Now, it can mean anything. Instead of using a certain word, plug in the word poonis.Its a much funnier definition and use of the word.
Dude, dont talk with poonis (food) in your mouth.
Hey, you dropped your poonis.(pencil)
Wake up and smell the poonis. (Coffee)
Hey, you dropped your poonis.(pencil)
Wake up and smell the poonis. (Coffee)
by Joshua Crespo September 14, 2005
Get the poonismug. 
by Bill Jaroszewski May 6, 2004
Get the poonismug. "Look at those poony drag queens!"
by Johnny Jonesman October 31, 2013
Get the poonymug. 