reducer

noun

1. a person or thing that reduces.
2. Photography.
   1. an oxidizing solution for lessening the density of an exposed negative.
   2. a developing agent.
3. (in plumbing) a coupling decreasing in diameter at one end.Compare increaser(def 2).

noun

1. photog a chemical solution used to lessen the density of a negative or print by oxidizing some of the blackened silver to soluble silver compoundsCompare intensifier (def. 3)
2. a pipe fitting connecting two pipes of different diameters
3. a person or thing that reduces