CSM meaning in Messaging ?

The Cigarette Smoking Man (abbreviated CSM or C-Man; sometimes referred to as Cancer Man or the Smoking Man) is a fictional character and one of the primary antagonists of the American science fiction drama television series The X-Files. He serves as the arch-nemesis of FBI Special Agent Fox Mulder. In the show's sixth season, his name is said to be C.G.B. Spender, but Dana Scully suggests this is one of "hundreds of aliases"; the show's characters and fans continue to refer to him by variations of "the Smoking Man" because he is almost always seen chain-smoking Morley cigarettes. In the eleventh season, he reveals his full name to be Carl Gerhard Busch.

Although he utters only four audible words in the entire first season of the show, the Smoking Man eventually develops into the series' primary antagonist. In his early appearances he is seen in the offices of Section Chief Scott Blevins and Assistant Director Walter Skinner, Mulder and his partner Dana Scully's supervisors. An influential man working for the powers that be, he is a key member in a government-conspiracy unit known only as the Syndicate, who are hiding the truth of alien existence and their plan to colonize Earth. His power and influence remain strong, even after most of the Syndicate is destroyed.

The Smoking Man is portrayed by Canadian actor William B. Davis. When Davis first took the role, the character was written as an extra for the pilot episode. He returned for small cameo appearances during the first season, making increasingly more appearances in the seasons that followed. Davis never received an award for his portrayal alone, but he was nominated for ensemble awards.

TV Guide included him in their 2013 list of The 60 Nastiest Villains of All Time.