throttle : Idioms & Phrases

• noun a hand-operated lever that controls the throttle valve
  

WordNet

• (Steam Engine), the hand lever by which a throttle valve is moved, especially in a locomotive.

Webster 1913

• noun a valve that regulates the supply of fuel to the engine
  throttle; accelerator.
  

WordNet

• (Steam Engine), a valve moved by hand or by a governor for regulating the supply of steam to the steam chest. In one form it consists of a disk turning on a transverse axis.

Webster 1913