"Shammered" is another way of describing someone who appears or is drunk.
Derived from the slang/phrase "Hammered," which also describes someone who is drunk, and the word "Shot," which, in drinking terms, describes some who is totally piss drunk "Shot," and is acting like a compete idiot because of it; therefore his mind is "shot." (Gone) (Done) (Finished) (Temporarily Fried)
Oh my god, Dom that guy is totally f*ucken "Shammered." He doesn't even know what he's doing or saying.