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2.
After ripping an ass explosion, the small fart(s) that come after it. Can often be smellier than the big one.
Keith kept farting through the whole damn movie, but his asstershocks were worse.
by bb+af June 26, 2010
 
1.
The shock that one gets while leaning forward to wipe after taking a dump and finding that the automatic flush thinks you have vacated ..... leaving a soggy ass.
Holy shit - that always happens. Now my ass is wet and shitty - I hate Ass-ter Shock

Or...

Why is that guys pants so wet? Must have been a victim of Ass-ter Shock
by The Brown Fox January 16, 2013