The Collaborative International Dictionary of English v.0.48:

Cut-off \Cut"-off`\ (k[u^]t"[o^]f`; 115), n.
   1. That which cuts off or shortens, as a nearer passage or
      road.
      [1913 Webster]

   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.
          [1913 Webster]