A Manpack is a Man worn by a Woman as a living backpack. Often seen at a Bar or nightclub an attractive woman may be observed with a man usually less attractive standing behind the woman with arms around her, or casually drapped over her shoulder in a "This belongs to me, and I am keeping it!" sort of way.
I would like to ask that Hot Babe to dance but we got to pry that Manpack off her first.....too much dead weight.
An everyday bag carried by a man which is larger than a purse but smaller than a backpack.
John didn't need to keep things in his wife's purse anymore. He had a Man-PACK.