Source : Webster's Revised Unabridged Dictionary (1913)

Reactionary \Re*ac"tion*a*ry\, a.
   Being, causing, or favoring reaction; as, reactionary
   movements.

Reactionary \Re*ac"tion*a*ry\, n.; pl. {Reactionaries}.
   One who favors reaction, or seeks to undo political progress
   or revolution.

Source : WordNet®

reactionary
     adj : extremely conservative [syn: {reactionist}, {far-right}]
     n : an extreme conservative; an opponent of progress or
         liberalism [syn: {ultraconservative}, {extreme
         right-winger}]