Entry 2 senses · 2 variants Webster, 1913 Reactionary /(-ā̇*ry̆)/ · Re·ac·tion·a·ry · IPA /ɹiˈæk.ʃəˌnɛɚ.i/ a. n. 01 a. Being, causing, or favoring reaction; as, reactionary movements. 1. Being, causing, or favoring reaction; as, reactionary movements. 02 n. One who favors reaction, or seeks to undo political progress or revolution. pl. Reactionaries ((-rĭz)) 1. One who favors reaction, or seeks to undo political progress or revolution.