personal best 

The quickest a person has ever successfully masturbated. Successful masturbations are for a guy: ejaculation, and for a girl: orgasm.

Jim started tugging on his weiner 4 seconds before he ejaculated, it was his personal best.

personal best by Brock Johnson January 4, 2008

Shitty personal best 

An individual is engaged in a strenuous activity and finds himself/herself in GI distress and on verge of defecating on oneself during said activity; individual still completes activity or event in a respectable time frame or other measurement. Used mostly when referring to athletic endeavor.

Runner: yo bitches I was cruising in my relay race on the A1A and rolling so hard I nearly shit my pants; unfortunately I had to ease up. Still ran a good time, it's my new shitty personal best.

Teammates: you better get yourself to a port a potty ASAP before you actually shit yourself. Just saying.

Shitty personal best by OG Baby Giraffe January 9, 2011