The most prestigious type of self gratification, a "mandela" is the act of masturbation while incarcerated. Due to the isolation and semi private room, the Mandela is a must for prison stays of any length. Named so aptly after Nelson Mandela who through years of jail time probably beat off over a speculated 100,000 times.
"Dude what did you do while you were in the drunk tank for 3 hours last night?"
"I just pulled a Mandela and passed out."