Full Combo, more commonly abbreviated as FC, is the term that refers to beating a song while correctly playing every note without overstrumming. This is different from simply scoring 100% on a song, since one can "break" (reset) their Multiplier, by overstrumming, and still play 100% of the notes. Every single song in the entire series has been FC'd by at least one person, with the exception of Exile and Trogdor (NTSC). Exile is impossible to FC (due to a glitch) and the NTSC version of Trogdor is also impossible due to the strumming speed of a part of the song exceeding the strum limit of the NTSC version of Guitar Hero II .
FBFC - also known as Full Band Full Combo, meaning that the maximum amount of people in a band (in a majority of cases, guitar, drums, bass, and vocals) FC a song without any duplicate instruments if the song does not include all four instruments.
OMBFC - One Man Band Full Combo, meaning that that each instrument has been FC'd by the same person.
FGFC - Full Game Full Combo, meaning that a player has FC'd every setlist song, not including DLC.
FSFC - Full Series Full Combo, meaning that a player has Full Game FC'd every game in a series. This has only happened three times as of 10/03/13. Marbler, KramRal, and GuitarHeroAddict112 were the 1st, 2nd, and 3rd players, respectively, to have accomplished this.