when placing a paper bag over an girl's head, and then proceeding to jizz in the bag and then shaking the bag around her head!! If left to Dry it will be very hard to remove the bag.
Dude 1: Dude why is she walking around with a paper bag on her head!
dude 2: Dude i gave her a milk bag but i forgot to tell her to take it off!!
The term used to describe a young man with a body shaped like a bag of milk. This man also tends to have a paler skin tone and usually, if not always, is downright ugly. Yet somehow this milk bag manages to get a hot girlfriend.
Guy 1: This girl is an absolute rocket.
Guy 2: Wow she is. Says she's in a relationship, check his Facebook.
Guy 1: Man this guy is a milk bag.
Guy 2: Standard.