n. A type of cycle that has only one wheel and is powered by pedals; it is most often used by acrobats.
v. To travel or move around by unicycle.
The Century Dictionary and Cyclopedia
n. A vehicle with only one wheel: a form of velocipede.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a vehicle with a single wheel that is driven by pedals
v. ride a unicycle
Word Usage
"But because a unicycle is always trying to fall over, most people cannot react quickly enough to control it, and no mechanical device had previously been able to."