Source : Webster's Revised Unabridged Dictionary (1913)

Utopian \U*to"pi*an\, a.
   Of or pertaining to Utopia; resembling Utopia; hence, ideal;
   chimerical; fanciful; founded upon, or involving, imaginary
   perfections; as, Utopian projects; Utopian happiness.

Utopian \U*to"pi*an\, n.
   An inhabitant of Utopia; hence, one who believes in the
   perfectibility of human society; a visionary; an idealist; an
   optimist. --Hooker.

Source : WordNet®

Utopian
     n : an idealistic (but usually impractical) social reformer; "a
         Utopian believes in the ultimate perfectibility of man"