Four-way cock Meaning, Definition & Usage

Definitions
  1. a cock connected with four pipes or ports, and having two or more passages in the plug, by which the adjacent pipes or ports may be made to communicate; formerly used as a valve in the steam engine, and now for various other purposes. In the illustration, a leads to the upper end of a steam engine cylinder, and b to the lower end; c is the steam pipe, and d the exhaust pipe.

Webster 1913