Source : Webster's Revised Unabridged Dictionary (1913)

Deep \Deep\, n.
   1. That which is deep, especially deep water, as the sea or
      ocean; an abyss; a great depth.

            Courage from the deeps of knowledge springs.
                                                  --Cowley.

            The hollow deep of hell resounded.    --Milton.

            Blue Neptune storms, the bellowing deeps resound.
                                                  --Pope.

   2. That which is profound, not easily fathomed, or
      incomprehensible; a moral or spiritual depth or abyss.

            Thy judgments are a great deep.       --Ps. xxxvi.
                                                  6.

   {Deep of night}, the most quiet or profound part of night;
      dead of night.

            The deep of night is crept upon our talk. --Shak.