Reducer /(-s?r)/

Re·du·cer

Reducer

n.
  1. One who, or that which, reduces.
  2. A contrivance for reducing the dimensions of one part so as to fit it to another, as a reducing coupling, or a device for holding a drilling a chuck. (Mach.)
  3. A reducing agent, either a developer or an agent for reducing density. (Photog.)
  4. a reducing agent. (Chem.)