2. The act of masturbating to a monster character(s).
3. To dress up like a monster and then proceed to masturbate.
2. Charlie has a monster fetish and has been caught in the act of monsterbation.
3. After a night of failed attempts with women on halloween, Charlie decided monsterbation in his zombie costume was the only way he'd get some.
the monster replaces master because one who subjects themselves to such acts are obviously dirty pigs.