An event where parkour practitioners (traceurs) gather together to 'jam', or do parkour. During one, everyone meets at a particular, set place, and jams it out there, and it can sometimes be followed by food and drink, or some form of sustenance, as the day has progressed and energy has been spent and needs must be replenished.
Traceur 1: "Dude, you coming to the Jam today?"
Traceur 2: "Of course, man! i wouldn't miss a Parkour Jam for ANYTHING!"
Traceur 1: "Brohammad! You coming to the Parkour Jam today?"
Guy: "Brobi-wan-kenobi, i couldn't do parkour if my life depended on it."
Traceur 1: "That's cool, there are always a few people tagging along just to watch because they aren't cool enough to do parkour."
guy: "Alright, Sweet!"