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A girlfriend whose girth is equal to that of a hippo, but has the ability to mask said girth to her boyfriend even though it is evident to the rest of the world.
Jordan: "what do you think of my new chick guys?"
Mike: "Where is she behind the fat chick?"
Jordan: "what do you mean?"
Mike: "dude, you have a Girlfriendoppotamus"
by Grob1782 February 11, 2011
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