The Collaborative International Dictionary of English v.0.48:

feudal \feu"dal\ (f[=u]"dal), a. [F. f['e]odal, or LL.
   feudalis.]
   1. Of or pertaining to feuds, fiefs, or fees; as, feudal
      rights or services; feudal tenures.
      [1913 Webster]

   2. Consisting of, or founded upon, feuds or fiefs; embracing
      tenures by military services; as, the feudal system.
      [1913 Webster]

WordNet (r) 3.0 (2006):

feudal
    adj 1: of or relating to or characteristic of feudalism [syn:
           feudal, feudalistic]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "feudal":
   absolute, absolutist, absolutistic, arbitrary, aristocratic,
   arrogant, authoritarian, authoritative, autocratic, bossy, client,
   dependent, despotic, dictatorial, domineering, feodal, feudatory,
   grinding, high-handed, imperative, imperial, imperious, inferior,
   liege, lordly, magisterial, magistral, manorial, masterful,
   monocratic, oppressive, overbearing, overruling, peremptory,
   praedial, real, repressive, seigneurial, seignioral, servile,
   severe, strict, subject, subordinate, subservient, suppressive,
   tributary, tyrannical, tyrannous, vassal



Bouvier's Law Dictionary, Revised 6th Ed (1856):

FEUDAL. A term applied to whatever concerned a feud; as feudal law: feudal
rights.