Meaning of REACTOR in English

n.1 a person or thing that reacts.

2 (in full nuclear reactor) an apparatus or structure in which a controlled nuclear chain reaction releases energy.

3 Electr. a component used to provide reactance, esp. an inductor.

4 an apparatus for the chemical reaction of substances.

5 Med. a person who has a reaction to a drug etc.

Oxford English vocab.      Оксфордский английский словарь.