Cut-offCut"-off`\ (k[u^]t"[o^]f`; 115), n. 1. That which cuts off or shortens, as a nearer passage or road. 2. (Mach.) (a) The valve gearing or mechanism by which steam is cut off from entering the cylinder of a steam engine after a definite point in a stroke, so as to allow the remainder of the stroke to be made by the expansive force of the steam already let in. See Expansion gear, under Expansion. (b) Any device for stopping or changing a current, as of grain or water in a spout.