Some creatures are so massive that their sheer bulk is a threat all of its own. Particularly massive monsters have an altogether devastating stomp.
A model with this special rule can make a Stomp in addition to its other close combat attacks (including). A Stomp has the special rule, and inflicts D6 (or D3 against lone Infantry models and skirmishers) automatic hits, at the model's Strength, on one enemy , or unit in base contact with the model and are randomised as . This represents the creature crushing the foe beneath its ponderous feet, or knocking their broken bodies aside with one sweep of its mighty tail (probably while it's roaring in a most intimidating fashion).
Unless specified, any special rules that apply to the model's normal attacks do not apply to its Stomps.