A list, literal or not, of those who are blackballed. Its most prominent use was in the US Red Scare of the post-WWII years - many performers and behind-the-scenes people were made industry unpersons overnight (see Martin Ritt's The Front, a fictionalized account of those days, in which Woody Allen - an alumnus of that era himself - plays a "front" for blacklisted writers). It's not limited to Hollywood, of course - any group can have a blacklist.