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A buttism is a statement or expression that just barely misses the mark/point of the conversation and may cause awkward looks or responses from an audience afterwards.
"Brad pitt is such a badass"

"i know right? he makes movies, sleeps with Angelina Jolie-"

"and gets her PREGNANT" (awkward looks)

-(the above pregnancy statement is a buttism)
by candyman/joecool February 04, 2010