Usually associated with consuming large quantities of semi-undigestables, such as corn or peanuts. The effect is a rapid-fire rectal discharge of the consumed food(s); often accompanied by diarrhea, accentuating the percieved effect.
"We had a great time at the picnic! There was lots of corn on the cob, but the next day I had a major case of machine bum!"
by franklore November 12, 2007