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1.
Jumping a BMX bike to flat or nearly flat from a high obstacle. Usually when riding street but it could happen riding skateparks or jumps. Used to describe before, during or after jumping.
"Dude are you going to jump down that?"
"Bone deth"
"Dude, I can see your femur. Are you okay?"
"Yeah dude bone deth!"
by cypruss July 17, 2012
 
2.
the inspration to do something extreme
"Dude jump off that roof on your bike." -Skateboarder
"Ok, BONE DETH!" -BMXer
"WHAT, you just jumped off that roof!" skateboarder
by Ajewyouknow January 02, 2012