Snifting

Snift´ing

a. & n.

1.

a. & n. from Snift. Snifting valve a small valve opening into the atmosphere from the cylinder or condenser of a steam engine, to allow the escape of air when the piston makes a stroke; - so called from the noise made by its action.

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