Definition.com
A Freethinker is one who is willing to use his mind without prejudice and without fearing to understand things that clash with his own customs, privileges, or beliefs. This state of mind is not common, but it is essential for right thinking.
Definition.com
A Freethinker is formerly a man who had been educated on ideas of religion, law, morality, and had arrived at free thought by virtue of his own struggle and toil. But now a new type of born freethinker has been appearing; one who has never even heard that there have been laws of morality and religion, and that there are authorities, but who simply grow up with negative ideas about everything, that is savages.