Any time you pedal as fast as you can while on a bike. Also, while you are "bike-sprinting", you do not change gears. This makes it different from just racing.
If you were trying to elude a wild man-eating dog that rips your shirt all the time you would probably us your bike to get away at high speed. Going as fast as you could would be bike-sprinting.
by Sean n Larenzo May 7, 2007