A sexual act that describes you dipping your cock into a pile of jizz, covering your cock in white jizz making it look like a snow cone hence the name, then stuffing your snow cone cock back into a girl's ass and screwing her so hard that you push her arms out from under her and hump her across the floor.
From Rules of Engagement Season 1 Episode 2
Russel: Alright, we both agree your fiance is a horn dog. Which is why I think we should ask for the Manitoba Snow Cone...
Adam: Stop saying 'we', okay? And I'm not asking for anything off of your list of humorously named... sex acts.