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1. A large rodent capable of eating a man.

2. A large rodent bent on world domination
1. Fatmouse+You=Fatmouse

2. (excerpt from Fatmouse website)Fatmouse is coming and he has a message and you are not going to like it. Fatmouse will consume your poor thin world and regurgitate it in his own image. Fatmouse Does not work fo ryou and he does not acknowledge your meager hopes and dreames. It is better to walk with Fatmouse than to be in his path, for Fatmouse must feed.
by dagg March 27, 2003
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What a guy has when he tries to penetrate while only half-hard. Comes from the visual similarity to a fat mouse trying to crawl through a small hole.
John told Suzie to work him a little longer before she mounted him, so that he wouldn't end up with fat mouse.
by JasonWS May 14, 2007
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A very old internet joke that doesn't seem to be dying. It is the counterpart to TubCat who was way cooler.
Fatmouse will consume you. He is in search of carbohydrates.
by Necromantix October 02, 2003
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