re·ac·tion·ar·y (rē-āk'shə-něr'ē) adj. Characterized by reaction, especially opposition to progress or liberalism; extremely conservative. n.
pl.re·ac·tion·ar·ies An opponent of progress or liberalism; an extreme conservative.
1840, on model of Fr. réactionnaire (19c.), from réaction (see reaction). In Marxist use, opposed to revolutionary and used opprobriously in ref. to opponents of communism (1858).