The marks of a cult define it as a cult and the four marks are:-
-human figurehead (ie Joseph Smith)
-new truth discovered
-new writings to accompany the bible (but in actual fact supercede the bible)
-"salvation" found only within the membership of that group.
-the belief that Christ's work is insufficient and needs to be suplemented in some way

Although cults are often thought of as small groups they do of course include bigger groups such as Mormons and JWs. However the biggest cult (and not always seen as such) is the RC church.

__________________
Stuart
Elder, Lambeg Baptist, Northern Ireland, UK

In Him the fulness of the Godhead dwells in bodily form and in Him you are complete (Col 2.9-10)

The sacrifice of a broken heart doth please Him but the sacrifice of a broken Christ alone doth satisfy Him (Richard Steele)