The Collaborative International Dictionary of English v.0.48:

Conceal \Con*ceal"\ (k[o^]n*s[=e]l"), v. t. [imp. & p. p.
   Concealed (k[o^]n*s[=e]ld"); p. pr. & vb. n. Concealing.]
   [OF. conceler, L. concelare; con- + celareto hide; akin to
   AS. helan, G. hehlen, E. hele (to cover), helmet. See Hell,
   Helmet.]
   To hide or withdraw from observation; to cover; to cover or
   keep from sight; to prevent the discovery of; to withhold
   knowledge of.
   [1913 Webster]

         It is the glory of God to conceal a thing. --Prov. xxv.
                                                  2.
   [1913 Webster]

         Declare ye among the nations, . . . publish and conceal
         not.                                     --Jer. l. 2.
   [1913 Webster]

         He which finds him shall deserve our thanks, . . .
         He that conceals him, death.             --Shak.

   Syn: To hide; secrete; screen; cover; disguise; dissemble;
        mask; veil; cloak; screen.

   Usage: To Conceal, Hide, Disguise, Dissemble,
          Secrete. To hide is the generic term, which embraces
          all the rest. To conceal is simply not make known what
          we wish to keep secret. In the Bible hide often has
          the specific meaning of conceal. See --1 Sam. iii. 17,
          18. To disguise or dissemble is to conceal by assuming
          some false appearance. To secrete is to hide in some
          place of secrecy. A man may conceal facts, disguise
          his sentiments, dissemble his feelings, secrete stolen
          goods.
          [1913 Webster]

                Bur double griefs afflict concealing hearts.
                                                  --Spenser.
          [1913 Webster]

                Both dissemble deeply their affections. --Shak.
          [1913 Webster]

                We have in these words a primary sense, which
                reveals a future state, and a secondary sense,
                which hides and secretes it.      --Warburton.
          [1913 Webster]

WordNet (r) 3.0 (2006):

concealing
    adj 1: covering or hiding; "the concealing darkness";
           "concealing curtains prevented discovery" [ant:
           revealing]
    n 1: the activity of keeping something secret [syn:
         concealment, concealing, hiding]