See first sentence of entry for tandem and cut in half. A bike for minimalists. Favoured by circus personnel. Users often fall prey to a Napoleon complex, opting for taller and taller models as the disease progresses.
The term unicycle is often used in robotics and control theory to mean a generalised cart or car moving in a two-dimensional world; these are also often called "unicycle-like" or "unicycle-type" vehicles. This usage is distinct from the literal sense of "one wheeled robot bicycle".