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1.
1. A gigantic, flabby, asymetrical, disgusting ass. Resembles a thundercloud due to its shapelessness, constant shifting, and that it strikes terror in the hearts of small children. Has been known to nuetralize erections and make beer taste flat.
2. A fart that echoes for at least 3 seconds.
1. I almost threw up when I saw that thunderbutt!
2. That thunderbutt was fucking nasty!
by Admiral Anarchy October 21, 2009
 
2.
A person (usually a woman) who's ass is so massive that when she walks her ass creates a thunderous rumble that frightens everyone around her.
Daaaaaaamn that womans ass is HUGE. She's got a Thunderbutt
by logicalkaos September 05, 2011
 
3.
the fat guy at the pound in homeward bound
sassy (the cat): "this way thunder butt"
by birdztheword May 30, 2009