Definition of reactionariness:
(adj) :
(politics) Extremely conservative; opposing revolution (such as the French Revolution); favoring a return to a "golden age" of the past.
(n) :
(politics) One who opposes revolution, wanting to reverse it, favoring a return to a past golden age. Often used as a derogatory by revolutionaires.
(adj) :
(chemistry) Of, pertaining to, participating in, or inducing a chemical reaction.
(adj) :
In reaction to; as a result of.