The Collaborative International Dictionary of English v.0.48:

Obscenity \Ob*scen"i*ty\, n.; pl. Obscenities. [L. obscentias:
   cf. F. obsc['e]nit['e].]
   That quality in words or things which presents what is
   offensive to chastity or purity of mind; obscene or impure
   lanquage or acts; moral impurity; lewdness; obsceneness; as,
   the obscenity of a speech, or a picture.
   [1913 Webster]

         Mr. Cowley asserts plainly, that obscenity has no place
         in wit.                                  --Dryden.
   [1913 Webster]

         No pardon vile obscenity should find.    --Pope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

obscenity
    n 1: the trait of behaving in an obscene manner [syn:
         obscenity, lewdness, bawdiness, salaciousness,
         salacity]
    2: an offensive or indecent word or phrase [syn: obscenity,
       smut, vulgarism, filth, dirty word]
    3: an obscene act