The Collaborative International Dictionary of English v.0.48:

Tormentor \Tor*ment"or\, n.
   1. One who, or that which, torments; one who inflicts penal
      anguish or tortures. --Jer. Taylor.
      [1913 Webster]

            Thoughts, my tormentors, armed with deadly stings.
                                                  --Milton.
      [1913 Webster]

   2. (Agric.) An implement for reducing a stiff soil,
      resembling a harrow, but running upon wheels. --Hebert.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tormentor
    n 1: someone who torments [syn: tormentor, tormenter,
         persecutor]
    2: a flat at each side of the stage to prevent the audience from
       seeing into the wings [syn: tormenter, tormentor,
       teaser]