The act of thrusting ones arm into a man or women's ass hole, once in the male/female pushes out explosive diarrhea which builds up and/or leaks out until the man or women pulls their fist out of the anus creating a blast of liquid shit.
"As Mark pulled his fist out Jordan's anal cavity liquid shit spewed all over Marks face, thus creating an Alabama arm cannon."
by FrozenSugarlumps December 19, 2013