a motor vehicle similar to a bicycle but usually larger and heavier, chiefly for one rider but sometimes having two saddles or an attached sidecar for passengers.
mo·tor·cy·cle (mō'tər-sī'kəl) n. A two-wheeled motor vehicle resembling a heavy bicycle, sometimes having two saddles and a sidecar with a third wheel.
[motor + (bi)cycle.] mo'tor·cy'cle v., mo'tor·cy'clist n.