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During a fart, when air is compressed between the grundle and a hard surface- the air erupts to the nearest exit, usually out the front of the crotch. It is thunderous, not just for the thunderous noise it makes, but also because of the unsettling direction of the blow.
I had a serious thunder grundle in math class, i think i sprained my taint.
by ceegee2 January 23, 2013
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