tri·cy·cle 
(trīsĭk′əl, -sĭ-kəl)
(trīsĭk′əl, -sĭ-kəl)n.
A vehicle, used especially by small children, that has three wheels, one at the front and two at the back, and is usually propelled by pedals.
[French : tri-, three (from Greek tri-; see TRI-) + Greek kuklos, wheel; see CYCLE.]