Ferocity is the state of being ferocious — wild, scary, and fierce. A five year-old girl pretending to be a lion will display her ferocity by roaring and baring her teeth.
Things known for their ferocity include wild animals, terrifying thunder storms, and fierce battlefield fights. A furious argument can have an element of ferocity, and so can a wild, loud piece of music. The Latin word ferus, which means "wild," is the root of not only ferocity, but ferocious and fierce. Ferocity came directly from the Latin ferocitatem, "fierceness, or wildness."