noun one who, or that which, reduces.
2. reducer ·add. ·noun a reducing valve.
3. reducer ·add. ·noun a reducing motion.
4. reducer ·add. ·noun a reducing agent, either a developer or an agent for reducing density.
5. reducer ·add. ·noun 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.
6. reducer ·add. ·noun a hydraulic device for reducing pressure and hence increasing movement, used to transmit the load from the hydraulic support of the lower shackle to the lever weighing apparatus in some kinds of heavy testing machines.