When you're playing Super Smash Brothers Brawl as Wario and accidentally make him ride his bike, which can often be a pain in the ass.
Example 1:

Person 1: Oh Crap, stupid Wario got on his bike!
Person 2: ACCIDENTAL BIKE!

Example 2:

Person 1: Aww man, I just accidental bike'd!
by Daini January 24, 2010
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