Definitions

Jud and I were arguing about whether a self-balancing unicycle is really a unicycle, and it led to our looking up the definitions of unicycle and bicycle on dictionary.com. (Hey, we're nerds; what can I say?) It turns out that the definition of bicycle is quite specific:

A vehicle consisting of a light frame mounted on two wire-spoked wheels one behind the other and having a seat, handlebars for steering, brakes, and two pedals or a small motor by which it is driven.

Go figure!