What is a "Blade Runner" anyway?

Blade Runners are specially trained policemen, like a detective and bounty hunter rolled into one, specialized in tracking down and retiring replicants.

The Blade Runner unit (officially known as "Rep-Detect") is a department of the Los Angeles Police Department specialized in locating and "retiring" (terminating, if you will) escaped replicants.

Why are they called "Blade Runners"? Where does the term come from?

The title can be traced back to a book by science fiction / fantasy writer Alan E. Nourse who wrote a story called "The Bladerunner". The story dealt with an impoverished society where medical supplies were so scarce they had to be supplied by smugglers known as "Blade Runners".

William S. Burroughs took the book and wrote "Bladerunner (A Movie)" in 1979. Similarities between Nourse's "The Bladerunner" and Scott's BR are in name only.

Ridley Scott felt that calling Deckard a "detective" just wouldn't do. Hampton Fancher, screenwriter for the movie, began searching through his personal library and came up with Burroughs' book.

Scott liked it, and he and Fancher also felt the title would make a great new title for the screenplay, and so they eventually bought the rights for the use of the name Blade Runner from both Nourse's and Burroughs' representatives.

So there you have it. The term "blade runner" is really best regarded as a code name; it doesn't really mean anything by itself. Also, the words echo "bounty hunter".

Note: Early versions of the script were titled "Android" and, later on, "Dangerous Days", before ultimately "Blade Runner" was chosen as the title.