The Collaborative International Dictionary of English v.0.48:

behaviorism \behaviorism\ n.
   an approach to psychology that emphasizes observable
   measurable behavior.

   Syn: behaviourism, behavioristic psychology, behaviouristic
        psychology.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

behaviorism
    n 1: an approach to psychology that emphasizes observable
         measurable behavior [syn: behaviorism, behaviourism,
         behavioristic psychology, behaviouristic psychology]