The Collaborative International Dictionary of English v.0.48:

Digester \Di*gest"er\, n.
   1. One who digests.
      [1913 Webster]

   2. A medicine or an article of food that aids digestion, or
      strengthens digestive power.
      [1913 Webster]

            Rice is . . . a great restorer of health, and a
            great digester.                       --Sir W.
                                                  Temple.
      [1913 Webster]

   3. A strong closed vessel, in which bones or other substances
      may be subjected, usually in water or other liquid, to a
      temperature above that of boiling, in order to soften
      them.
      [1913 Webster]

WordNet (r) 3.0 (2006):

digester
    n 1: autoclave consisting of a vessel in which plant or animal
         materials are digested