When ones sphinster muscle has been clenched for an extended period of time causing the sphincter muscle to contract and relax rapidly thus resulting in loss of clenching ability where by feces is released through the anus.
While Greg was boating in the middle of Lake Arthur he had to poop, he clenched for so long that he finally succumbed to sphincter fatigue and shit his shorts!
by butch8069 August 31, 2011
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