Vulgarity, n.
Etymology: [Cf. F. vulgarité, L. vulgaritas the multitude.]
1. The quality or state of being vulgar; mean condition of life; the state of the lower classes of society. Sir T. Browne.
2. Grossness or clownishness of manners of language; absence of refinement; coarseness. The reprobate vulgarity of the frequenters of Bartholomew Fair. B. Jonson.
Shades of meaning
Fernald has no entry of its own for vulgarity; he lists it under slang.
He lists it without comment; the entries above explain its neighbors.