The Collaborative International Dictionary of English v.0.48:

Dehumanize \De*hu"man*ize\, v. t.
   To divest of human qualities, such as pity, tenderness, etc.;
   as, dehumanizing influences.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dehumanize
    v 1: deprive of human qualities; "Life in poverty has
         dehumanized them" [syn: dehumanize, dehumanise] [ant:
         humanise, humanize]
    2: make mechanical or routine [syn: dehumanize, dehumanise]