noun.
One who is occupied with ideas or ideals that have no real significance or value; one who indulges in theories or speculations, or fabricates ideal schemes.
noun.
One who advocates the doctrines of ideology.
the GNU version of the Collaborative International Dictionary of English
noun.
One who treats of ideas; one who theorizes or idealizes; one versed in the science of ideas, or who advocates the doctrines of ideology.