The Collaborative International Dictionary of English v.0.48:

free association \free association\ n. (psychoanalysis)
   The act or process of free-associating. It is a technique
   used in psychoanalysis and is supposed to allow the analyst
   access to the unconscious thoughts of the analysand. See
   free-associate.
   [PJC]

WordNet (r) 3.0 (2006):

free association
    n 1: a thought process in which ideas (words or images) suggest
         other ideas in a sequence