n. 1. One who, or that which, develops. [ 1913 Webster ]
2. (Photog.) A chemical bath or reagent used in developing photographs. By the action of the developer, the latent image on a photographic plate or film, not perceptible to the eye after exposure in the camera, is developed and becomes visible. [ 1913 Webster +PJC ]
3. (Dyeing) A reagent used to produce an ingrain color by its action upon some substance on the fiber. [ Webster 1913 Suppl. ]
4. a corporation or individual who finances or organizes a real estate development{ 5 }. [ PJC ]