Source : Webster's Revised Unabridged Dictionary (1913)

Radicalism \Rad"i*cal*ism\, n. [Cf. F. radicalisme.]
   The quality or state of being radical; specifically, the
   doctrines or principles of radicals in politics or social
   reform.

         Radicalism means root work; the uprooting of all
         falsehoods and abuses.                   --F. W.
                                                  Robertson.

Source : WordNet®

radicalism
     n : the political orientation of those who favor revolutionary
         change in government and society