Source : Webster's Revised Unabridged Dictionary (1913)

Polygraph \Pol"y*graph\, n. [Gr. ? writing much; poly`s much,
   many + ? to write: cf. F. polygraphe.]
   1. An instrument for multiplying copies of a writing; a
      manifold writer; a copying machine.

   2. In bibliography, a collection of different works, either
      by one or several authors. --Brande & C.

Source : WordNet®

polygraph
     n : a medical instrument that records several physiological
         processes simultaneously (e.g., pulse rate and blood
         pressure and respiration and perspiration)