When one masturbates to pornographic material that's extremely perturbing, raunchy, disgusting, or so obscurely erotic that it is hard to consider it "porn".
Perturbation is NOT a synonym to disturbation, which refers to the methodology of masturbation rather than the subject matter.
I was perturbating to A Japanese Woman Fries An Egg And Asks You About Your Day the other day and right after I finished I realized how screwed up it was.
...Then I did it again the next night and came to the same horrible revelation.
Perturbation is so great.