"RoboSam" is a term fans and reviewers use to describe Sam in season 6. Another term used is Soulless!Sam or Not!Sam. It was made canon in the show as well in a few scenes, as quotes from Dean.
This could be a reference to the character Robocop. Robocop was the main character in a movie of the same name about a cop who is wounded and then made into a powerful cyborg. Dean also calls Sam "RoboSam" in 6.07 Family Matters.