Source : Webster's Revised Unabridged Dictionary (1913)

Freethinking \Free"think`ing\, n.
   Undue boldness of speculation; unbelief. --Berkeley. -- a.
   Exhibiting undue boldness of speculation; skeptical.

Source : WordNet®

freethinking
     n : the doctrine that reason is the right basis for regulating
         conduct [syn: {rationalism}]