When you're going hard in the back and you start to blow it and leave half inside and the rest caked on the buns.
You creme fill the bun and layer the icing on the bun, thus being a jambuster.
by runner52 January 17, 2012
From Manitoba, Canada, it means a Jelly filled donut.
The filling squirted out, as he ate the Jambuster.
by Kody B August 03, 2004
Adjusting one's cock to make a hardon more comfortable. Usually neccessary as the result of a log jam caused by erotic sights such as up skirt or down blouse viewing. The discomfort of the log jam may force a jam buster in public, in which case it has to be done as fast and as discretly as possible.
I got so darn hard at work the other day looking up this girls skirt, I just had to do a "jam buster" to let my cock stand up. I looked around to see if anyone was looking, then as quickly as possible, I put my hand down the front of my jeans and freed my cock.
by Mickeymysterious1 April 25, 2009