Source : Webster's Revised Unabridged Dictionary (1913)

Hidden \Hid"den\, p. p. & a.
   from {Hide}. Concealed; put out of view; secret; not known;
   mysterious.

   {Hidden fifths} or {octaves} (Mus.), consecutive fifths or
      octaves, not sounded, but suggested or implied in the
      parallel motion of two parts towards a fifth or an octave.

   Syn: {Hidden}, {Secret}, {Covert}.

   Usage: Hidden may denote either known to on one; as, a hidden
          disease; or intentionally concealed; as, a hidden
          purpose of revenge. Secret denotes that the thing is
          known only to the party or parties concerned; as, a
          secret conspiracy. Covert literally denotes what is
          not open or avowed; as, a covert plan; but is often
          applied to what we mean shall be understood, without
          openly expressing it; as, a covert allusion. Secret is
          opposed to known, and hidden to revealed.

                Bring to light the hidden things of darkness.
                                                  --1 Cor. iv.
                                                  5.

                My heart, which by a secret harmony Still moves
                with thine, joined in connection sweet.
                                                  --Milton.

                By what best way, Whether of open war, or covert
                guile, We now debate.             --Milton.