The Collaborative International Dictionary of English v.0.48:

Insincerity \In`sin*cer"i*ty\, n. [Cf. F. insinc['e]rit['e].]
   The quality of being insincere; lack of sincerity, or of
   being in reality what one appears to be; dissimulation;
   hypocritical; deceitfulness; hollowness; untrustworthiness;
   as, the insincerity of a professed friend; the insincerity of
   professions of regard.
   [1913 Webster]

         What men call policy and knowledge of the world, is
         commonly no other thing than dissimulation and
         insincerity.                             --Blair.
   [1913 Webster]

WordNet (r) 3.0 (2006):

insincerity
    n 1: the quality of not being open or truthful; deceitful or
         hypocritical [syn: insincerity, falseness,
         hollowness] [ant: sincerity]

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "insincerity":
   Tartuffery, Tartuffism, affectation, affectedness, airs,
   airs and graces, apparent soundness, artfulness, artificiality,
   cant, casuistry, circularity, craftiness, credibility gap,
   crossed fingers, deceitfulness, disingenuousness, distortion,
   emptiness, equivocalness, equivocation, evasive reasoning, facade,
   fallaciousness, fallacy, false front, false piety, false show,
   falseheartedness, falseness, feigned belief, flattering tongue,
   forswearing, fraud, front, goody-goodiness, gush, hollow mockery,
   hollowness, hypocrisy, image, intrigue, jesuitism, jesuitry,
   mannerism, mealymouthedness, mere show, misapplication, mockery,
   mummery, mystification, obfuscation, obscurantism, oiliness,
   oversubtlety, perjury, perversion, pharisaicalness, pharisaism,
   philosophism, pietism, pietisticalness, piety, piousness,
   plausibility, plausibleness, pretense, pretension,
   prunes and prisms, public image, put-on, putting on airs,
   rationalization, religionism, religiosity, sanctimoniousness,
   sanctimony, self-righteousness, sham, sharp practice, show,
   slobber, smarm, snivel, snuffle, sophism, sophistical reasoning,
   sophistication, sophistry, special pleading, speciosity,
   specious reasoning, speciousness, stylishness, subtlety,
   that flattering unction, tongue in cheek, uncandidness, uncandor,
   unction, unctuousness, unfrankness, unnaturalness, unsincereness,
   untruthfulness, vicious circle, vicious reasoning