The Collaborative International Dictionary of English v.0.48:

Blencher \Blench"er\, n.
   1. One who, or that which, scares another; specifically, a
      person stationed to prevent the escape of the deer, at a
      hunt. See Blancher. [Obs.]
      [1913 Webster]

   2. One who blenches, flinches, or shrinks back.
      [1913 Webster]