The Collaborative International Dictionary of English v.0.48:

Aristotelian \Ar`is*to*te"li*an\ (?; 277), a.
   Of or pertaining to Aristotle, the famous Greek philosopher
   (384-322 b. c.). -- n. A follower of Aristotle; a
   Peripatetic. See Peripatetic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Aristotelian
    adj 1: of or relating to Aristotle or his philosophy;
           "Aristotelean logic" [syn: Aristotelian,
           Aristotelean, Aristotelic, peripatetic]
    n 1: a follower of Aristotle or an adherent of Aristotelianism
         [syn: Aristotelian, Aristotelean, Peripatetic]