"Base Form" is a term used in the OBD to denote a character at his barest stats. In fiction, most notably shounen manga, characters start off with standard set of stats and as the story progresses they get a number of power ups, most usually in the form of transformations of some sort. When a thread starter specifies the use of a base form all feats not performed while in that form should not be used. Examples are Goku, who starts out fairly strong but stacks up power ups in the way of Super Sayian. Naruto's powerups are Kyuubi and the Sage technique, Bleach has Shikai, Bankai, and Vaizard Masks. While One Piece for example, has Luffy using gears.