Meaning of REACTION in English
n. 1 the act or an instance of reacting; a responsive or reciprocal action. 2 a a responsive feeling (what was your reaction to the news?). b an immediate or first impression. 3 the occurrence of a (physical or emotional) condition after a period of its opposite. 4 a bodily response to an external stimulus, e.g. a drug. 5 a tendency to oppose change or to advocate return to a former system, esp. in politics. 6 the interaction of substances undergoing chemical change. 7 propulsion by emitting a jet of particles etc. in the direction opposite to that of the intended motion. reactionist n. & adj.
[ REACT + -ION or med.L reactio (as RE-, ACTION) ]
Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012