Ex-păn'sion-gēar, n.

n. (Steam-eng.) A cut-off. [See Illustr. of Link-motion.]

Fixed expansion-gear, or fixed cut-off, one that always operates at the same fixed point of the stroke. — Variable or adjustable expansion-gear or cut-off, one that may be made to operate at different points of the stroke, while the engine is in motion. — Automatic expansion-gear or cut-off, one that is regulated by the governor, and varies the supply of steam to the engine with the demand for power.