reactor

Short definition from Wiktionary

Noun

1. 1
   A person who responds to a suggestion, stimulation or other influence.
2. 2
   A structure used to contain chemical or other reactions.
3. 3
   A device which uses atomic energy to produce heat.
4. 4
   A chemical substance which responds to the presence of, or contact with, another substance.
5. 5
   An electrical component with reactance