The Collaborative International Dictionary of English v.0.48:

Depth \Depth\ (s[e^]pth), n. [From Deep; akin to D. diepte,
   Icel. d[=y]pt, d[=y]p[eth], Goth. diupi[thorn]a.]
   1. The quality of being deep; deepness; perpendicular
      measurement downward from the surface, or horizontal
      measurement backward from the front; as, the depth of a
      river; the depth of a body of troops.
      [1913 Webster]

   2. Profoundness; extent or degree of intensity; abundance;
      completeness; as, depth of knowledge, or color.
      [1913 Webster]

            Mindful of that heavenly love
            Which knows no end in depth or height. --Keble.
      [1913 Webster]

   3. Lowness; as, depth of sound.
      [1913 Webster]

   4. That which is deep; a deep, or the deepest, part or place;
      the deep; the middle part; as, the depth of night, or of
      winter.
      [1913 Webster]

            From you unclouded depth above.       --Keble.
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            The depth closed me round about.      --Jonah ii. 5.
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   5. (Logic) The number of simple elements which an abstract
      conception or notion includes; the comprehension or
      content.
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   6. (Horology) A pair of toothed wheels which work together.
      [R.]
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   7. (A["e]ronautics) The perpendicular distance from the chord
      to the farthest point of an arched surface.
      [Webster 1913 Suppl.]

   8. (Computers) the maximum number of times a type of
      procedure is reiteratively called before the last call is
      exited; -- of subroutines or procedures which are
      reentrant; -- used of call stacks.
      [PJC]

   Depth of a sail (Naut.), the extent of a square sail from
      the head rope to the foot rope; the length of the after
      leach of a staysail or boom sail; -- commonly called the
      drop of a sail.
      [1913 Webster]

WordNet (r) 3.0 (2006):

depth
    n 1: the extent downward or backward or inward; "the depth of
         the water"; "depth of a shelf"; "depth of a closet" [syn:
         depth, deepness]
    2: degree of psychological or intellectual profundity
    3: (usually plural) the deepest and most remote part; "from the
       depths of darkest Africa"; "signals received from the depths
       of space"
    4: (usually plural) a low moral state; "he had sunk to the
       depths of addiction"
    5: the intellectual ability to penetrate deeply into ideas [syn:
       astuteness, profundity, profoundness, depth,
       deepness]
    6: the attribute or quality of being deep, strong, or intense;
       "the depth of his breathing"; "the depth of his sighs," "the
       depth of his emotion"