Verb. The act of partaking in masturbational activity using a baseball mitt. One must tenderize their preferred mitt and likewise toughen the area to be stimulated in order for successful mittsturbation to occur. After many sessions with one's mitt, the mitt will be considered "broken-in". Each session brings the mittsturbator closer to this desired state of mitt. This is an extremely advanced technique in terms of self stimulation, and should only be exercised when one considers himself (or her...self..) ready. Prerequisite: one must be a major league masturbator in order to commence in minor league mittsturbating.
John mittsturbated with his new Easton glove, which ultimately resulted in a pop-fly to center field.
Stanley asked his girlfriend to mittsturbate him. Unfortunately, she could not because she did not own a left-handed glove.