A combination of the words "probability" and "calculation." It is therefore a calculation of the probability of an event. High-profile scientists and forensic detectives use this word all the time in that it increases their verbal efficiency by approximately 3.5%. It can also be used in the verb form (probulate)
When one goes an extended period of time without jerking off. Most will give in to willpower and natural urges, but the courageous and strong can sometimes go for days or weeks without choking the chicken. See The Contest (Seinfeld).