reactionary

Short definition from Wiktionary

Adjective

1. 1
   Extremely conservative; opposing revolution (such as the French Revolution); favoring a return to a golden age of the past.
2. 2
   Of, pertaining to, participating in, or inducing a chemical reaction.
3. 3
   In reaction to; as a result of.

Noun

1. 1
   One who opposes revolution, wanting to reverse it, favoring a return to a past golden age. Often used as a derogatory by revolutionaires.