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1.
Similar to the Chicago Mustache, except the person on the bottom is wearing a snowsuit and the person on the top has drank milk all day instead of eating corn.
I was watching "How I met your mother" and got so turned on that the next day I only drank milk and then gave your mother a Manitoba Milkbag that night!
by ski9600 August 31, 2009
 
2.
It is a canadian sex act where milking girl is on all fours, with her breasts hanging in free air, then they are milked like a cow, with occasionally giving her nipple crunch, and some light punches in the breasts. To make it more interesting usually a man also does the girl in her ass in doggie style during this.
When she said she had delivered baby just a few months ago, the gang got excited to do Manitoba milk bag with her
by Killer Gunshot November 25, 2010