From The Collaborative International Dictionary of English v.0.48 [gcide]:
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]
From WordNet (r) 3.0 (2006) [wn]:
Freemason
n 1: a member of a widespread secret fraternal order pledged to
mutual assistance and brotherly love [syn: Freemason,
Mason]