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

Moby Thesaurus II by Grady Ward, 1.0:

142 Moby Thesaurus words for "obscenity":
   Rabelaisianism, X-rated movie, abominability, animality,
   bad language, baseness, bawdiness, bawdry, beastliness,
   billingsgate, blue language, blue movie, carnality, clitoromania,
   coarseness, colorful language, concupiscence, contemptibility,
   contrariety, crassness, crudeness, crudity, curse, cursing, cuss,
   cuss word, cussing, despicability, despicableness, dirt, dirtiness,
   dirty language, dirty movie, dirty name, dirty talk, dirty word,
   disgustingness, dysphemism, earthiness, epithet, erotic art,
   erotic literature, eroticism, eroticomania, erotographomania,
   erotomania, evil speaking, expletive, fescenninity, filth,
   filthiness, filthy language, fleshliness, foul invective,
   foul language, foulness, fulsomeness, furor uterinus, gaudiness,
   goatishness, grossness, gynecomania, harshness, hatefulness,
   heinousness, horniness, hysteromania, iconolagny, ignobility,
   lasciviousness, lecherousness, lechery, lewdness, libidinousness,
   lickerishness, loathsomeness, loudness, lubriciousness, lubricity,
   lust, lustfulness, meretriciousness, nastiness, naughty word,
   nauseousness, no-no, noisomeness, noxiousness, nymphomania, oath,
   objectionability, objectionableness, obnoxiousness, odiousness,
   offensiveness, pornographic art, pornographic literature,
   pornographomania, pornography, profane oath, profane swearing,
   profanity, prurience, pruriency, putridity, putridness, randiness,
   rawness, rebarbativeness, repellence, repellency, repugnance,
   repulsiveness, ribaldry, rottenness, roughness, rudeness,
   salaciousness, salacity, satyriasis, satyrism, scatology,
   scurrility, sensuality, sexiness, sexploitation, sexuality,
   skin flick, smut, smuttiness, soft-core pornography, stag film,
   strong language, swearing, swearword, unparliamentary language,
   unrepeatable expressions, unspeakableness, uteromania,
   vile language, vileness, vulgar language



Bouvier's Law Dictionary, Revised 6th Ed (1856):

OBSCENITY, crim. law. Such indecency as is calculated to promote the
violation of the law, and the general corruption of morals.
     2. The exhibition of an obscene picture is an indictable offence at
common law, although not charged to have been exhibited in public, if it be
averred that the picture, was exhibited to sundry persons for money. 2 Serg.
& Rawle, 91.