The Collaborative International Dictionary of English v.0.48:

Solecism \Sol"e*cism\, n.[F. sol['e]cisme, L. soloecismus, Gr.
   soloikismo`s, fr. soloiki`zein to speak or write incorrectly,
   fr. so`loikos speaking incorrectly, from the corruption of
   the Attic dialect among the Athenian colonists of So`loi in
   Cilicia.]
   1. An impropriety or incongruity of language in the
      combination of words or parts of a sentence; esp.,
      deviation from the idiom of a language or from the rules
      of syntax.
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            A barbarism may be in one word; a solecism must be
            of more.                              --Johnson.
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   2. Any inconsistency, unfitness, absurdity, or impropriety,
      as in deeds or manners.
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            Caesar, by dismissing his guards and retaining his
            power, committed a dangerous solecism in politics.
                                                  --C.
                                                  Middleton.
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            The idea of having committed the slightest solecism
            in politeness was agony to him.       --Sir W.
                                                  Scott.
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   Syn: Barbarism; impropriety; absurdity.
        [1913 Webster]

WordNet (r) 3.0 (2006):

solecism
    n 1: a socially awkward or tactless act [syn: faux pas,
         gaffe, solecism, slip, gaucherie]