An I-Mosh Fat Guy is that 1 very large dude you find in a mosh pit at a rock/metal/punk concert. It's always that 1 guy that pushes you. You aren't necessarily afraid of him but you hate having to deal with him.
Hey dude, why do you have that black eye?

Oh, I got smacked in the face by an I-Mosh Fat Guy at the concert last night.
by xxguitarxmetalxx666 March 6, 2010
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