Four-way cock

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.

See also: Four-way

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.