The Collaborative International Dictionary of English v.0.48:

Brutalize \Bru"tal*ize\, v. t. [imp. & p. p. Brutalized; p.
   pr. & vb. n. Brutalizing.] [Cf. F. brutaliser.]
   To make brutal; beasty; unfeeling; or inhuman.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Brutalize \Bru"tal*ize\, v. i.
   To become brutal, inhuman, barbarous, or coarse and beasty.
   [R.]
   [1913 Webster]

         He mixed . . . with his countrymen, brutalized with
         them in their habits and manners.        --Addison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

brutalize
    v 1: treat brutally [syn: brutalize, brutalise]
    2: make brutal, unfeeling, or inhuman; "Life in the camps had
       brutalized him" [syn: brutalize, brutalise, animalize,
       animalise]
    3: become brutal or insensitive and unfeeling [syn: brutalize,
       brutalise, animalize, animalise]