The Collaborative International Dictionary of English v.0.48:

Concealment \Con*ceal"ment\, n. [OF. concelement.]
   1. The act of concealing; the state of being concealed.
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            But let concealment, like a worm i' the bud,
            Feed on her damask cheek.             --Shak.
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            Some dear cause
            Will in concealment wrap me up awhile. --Shak.
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   2. A place of hiding; a secret place; a retreat frem
      observation.
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            The cleft tree
            Offers its kind concealment to a few. --Thomson.
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   3. A secret; out of the way knowledge. [Obs.]
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            Well read in strange concealments.    --Shak.
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   4. (Law) Suppression of such facts and circumstances as in
      justice ought to be made known. --Wharton.
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WordNet (r) 3.0 (2006):

concealment
    n 1: the condition of being concealed or hidden [syn: privacy,
         privateness, secrecy, concealment]
    2: a covering that serves to conceal or shelter something; "a
       screen of trees afforded privacy"; "under cover of darkness";
       "the brush provided a covert for game"; "the simplest
       concealment is to match perfectly the color of the
       background" [syn: screen, cover, covert, concealment]
    3: the activity of keeping something secret [syn: concealment,
       concealing, hiding]