The Collaborative International Dictionary of English v.0.48:

Bencher \Bench"er\, n.
   1. (Eng. Law) One of the senior and governing members of an
      Inn of Court.
      [1913 Webster]

   2. An alderman of a corporation. [Eng.] --Ashmole.
      [1913 Webster]

   3. A member of a court or council. [Obs.] --Shak.
      [1913 Webster]

   4. One who frequents the benches of a tavern; an idler.
      [Obs.]
      [1913 Webster] benchmark

Bouvier's Law Dictionary, Revised 6th Ed (1856):

BENCHER, English law. A bencher is a senior in the inns of court, entrusted
with their government and direction.