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1.
To masturbate by inserting one's fist into one's own orifice or orifices. Artificial or disembodied fists may also be used. The word is a hybrid of "Fisting", "Masturbating" and "Sophisticated", and as such could be considered a sophisticated form of self-fisting.
"I wouldn't go in there Gavin, Tylah is Fisturbating."

Bryce: "Dan, if you don't sort that shit out my fist will be up your ass"
Dan: "I can fisturbate MYSELF!"
by Under Training April 26, 2008