bi·cy·cle 
(bīsĭk′əl, -sĭ-kəl, -sī′kəl)
(bīsĭk′əl, -sĭ-kəl, -sī′kəl)n.
1. A vehicle consisting of a light frame mounted on two typically wire-spoked wheels one behind the other and usually having a seat, handlebars for steering, brakes, and two pedals by which it is driven.
2. An exercise bicycle.
intr.v. bi·cy·cled, bi·cy·cling, bi·cy·cles
To ride or travel on a bicycle.
[Probably BI-1 + -cycle (on the model of TRICYCLE, three-wheeled coach).]
bicy·cler (-klər), bicy·clist (-klĭst) n.