Source : Webster's Revised Unabridged Dictionary (1913)

Injector \In*ject"or\, n.
   1. One who, or that which, injects.

   2. (Mach.) A contrivance for forcing feed water into a steam
      boiler by the direct action of the steam upon the water.
      The water is driven into the boiler by the impulse of a
      jet of the steam which becomes condensed as soon as it
      strikes the stream of cold water it impels; -- also called
      {Giffard's injector}, from the inventor.