purging-cockn. now rare = purge cockn. at purgev.1 Compounds.
ΚΠ
1875 E. H. KnightAmer. Mech. Dict. III. 1836/1Purging-cock, the mud-cock or discharge-valve of a steam-boiler.
1909 Horseless Age 3 Feb. 172/2 It is fitted with a purging cock, so that the whole system may be drained, the pump being at the lowest point of the system.