The Collaborative International Dictionary of English v.0.48:

dissimulation \dis*sim`u*la"tion\, n. [L. dissimulatio: cf. F.
   dissimulation.]
   The act of dissembling; a hiding under a false appearance;
   concealment by feigning; false pretension; hypocrisy.
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         Let love be without dissimulation.       --Rom. xii. 9.
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         Dissimulation . . . when a man lets fall signs and
         arguments that he is not that he is.     --Bacon.
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         Simulation is a pretense of what is not, and
         dissimulation a concealment of what is.  --Tatler.
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WordNet (r) 3.0 (2006):

dissimulation
    n 1: the act of deceiving [syn: deception, deceit,
         dissembling, dissimulation]