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3.
Someone who is being either annoying, inappropriate, or an asshole.
Suck vage, you're being a buttmonster.
by poopcock November 18, 2007
 
1.
An alternate name for a demon (or "pinky demon") in ID Software's original Doom game series.
Blood and viscera flew everywhere when I attacked the group of butt monsters with my chainsaw.
by Timotheus325 January 21, 2009
 
2.
An oversized 'butt plug'. See 'Butt Plug'
You, me, the Butt Monster. Saturday night. Be prepared
by MKULTRA July 07, 2013
 
4.
somone who loves it in the butt.
David: "Chris.......no matter what, you always seem to have sex with that chick in the butt."

Chris: "I know dude, that's why we call her the butt monster!
by jj887732 November 10, 2006