The Collaborative International Dictionary of English v.0.48:

Freemason \Free"ma`son\, n.
   One of an ancient and secret association or fraternity, said
   to have been at first composed of masons or builders in
   stone, but now consisting of persons who are united for
   social enjoyment and mutual assistance.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Freemason
    n 1: a member of a widespread secret fraternal order pledged to
         mutual assistance and brotherly love [syn: Freemason,
         Mason]