speed wobbles 

When a skateboard begins to tightly swerve back and forth from left to right with increasing velocity until the skateboard begins to undulate so rapidly that the rider is usually thrown from the board.

I was doing some downhill skateboarding and I went so fast that I got the speed wobbles and got pitched into the street.

speed wobbles by Marcus Solomon December 3, 2007

speed wobbles 

A state of shakiness a rider experiences while hitting a high speed on a board typically accompanied by an adrenaline rush and/or a state of panic.

Dude: Dude, bro, I would have totally stuck that turn but I got the speed wobbles half way down the hill and I knew it was time to bail!
Dude, bro: Poser...

speed wobbles by Molly C August 22, 2006

Speed Wobble 

When a "chubby" person hits their maximum speed potential and begins to wobble, the wobble usually results in the "speed wobble" subject on the floor in a fat heap. in Pain. Crying. Sweating.

Kid1: Oh damn dude, that kid just totally had a speed wobble!
Kid2: Yeah! I think he poo'd himself too.

Speed Wobble by ReinventingTheEnglishLanguage August 25, 2010