Blade Runner is a term part of the titular special police task force. The main purpose of Blade Runners is to eliminate replicants
Their duty is to identify, hunt, and "retire" (kill) replicants who have arrived on Earth illegally. The reason for the reference to them as "blade runners" was never explained in the film.
Behind the Scenes Edit
The term "Blade Runner" originates not from any works by Phillip K. Dick but from a little known 1974 novella by Alan E. Nourse. This novel was called The Bladerunner and in the novel, the reason for the term is given. Bladerunners (the term is one word in this novel) are black market medical suppliers for underground physicians. The term appears to refer to the scalpel blade, a picture of a medical scalpel is prominently on the book cover illustration.