The Collaborative International Dictionary of English v.0.48:

Feudalize \Feu"dal*ize\, v. t. [imp. & p. p. Feudalized; p.
   pr. & vb. n. Feudalizing.]
   To reduce to a feudal tenure; to conform to feudalism.
   [1913 Webster]

WordNet (r) 3.0 (2006):

feudalize
    v 1: bring (a country or people) under feudalism