An ass attack is when you are feeling completely normal without the feeling of having to take a shit. Then all of a sudden out of nowhere you have to shit and shit BAD!! You pretty much have less than one minute to find a toilet. It can happen anytime or anywhere.

the sudden attack of the anus

the runs, diarrhea

Giving it hard, deep and fast in your anal orfice

When a man unexpectdly gives another man anal.

to become sudddenly very emotional - surprised, angry etc.
to have an ass attack = to flip out

A homosexual man who pounds ones sphincter until it is so sore one feels that their ass is on fire