spec script noun (spec is short for "speculation")
A spec script is a script (or screenplay), for TV or film, that is written without a contract, by the initiative of a writer.
There are two main uses of, or reasons for writing, a spec script:
(1) A script written without a contract with the hope that it can be sold to a studio or producer.
(2) A script used by a writer to show off their talent and used with, or as, a resume to gain the attention of a studio or producer with the hopes of being hired as a writer.
Example: Ken Keeler wrote a spec script for the Simpsons, and was soon hired as a full time writer.