instroke

An inward stroke, especially a piston stroke moving away from the crankshaft.

In an engine, that stroke during which the plunger enters into the cylinder; in a single-acting engine, the exhaust stroke.

An inward stroke; specif., in a steam or other engine, a stroke in which the piston is moving away from the crank shaft; — opposed to outstroke.

the stroke of an engine piston moving away from the crankshaft