A deep line of operations

Deep \Deep\ (d[=e]p), a. [Compar. {Deeper} (d[=e]p"[~e]r);
   superl. {Deepest} (d[=e]p"[e^]st).] [OE. dep, deop, AS.
   de['o]p; akin to D. diep, G. tief, Icel. dj[=u]pr, Sw. diup,
   Dan. dyb, Goth. diups; fr. the root of E. dip, dive. See
   {Dip}, {Dive}.]
   1. Extending far below the surface; of great perpendicular
      dimension (measured from the surface downward, and
      distinguished from high, which is measured upward); far to
      the bottom; having a certain depth; as, a deep sea.
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            The water where the brook is deep.    --Shak.
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   2. Extending far back from the front or outer part; of great
      horizontal dimension (measured backward from the front or
      nearer part, mouth, etc.); as, a deep cave or recess or
      wound; a gallery ten seats deep; a company of soldiers six
      files deep.
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            Shadowing squadrons deep.             --Milton.
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            Safely in harbor
            Is the king's ship in the deep nook.  --Shak.
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   3. Low in situation; lying far below the general surface; as,
      a deep valley.
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   4. Hard to penetrate or comprehend; profound; -- opposed to
      {shallow} or {superficial}; intricate; mysterious; not
      obvious; obscure; as, a deep subject or plot.
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            Speculations high or deep.            --Milton.
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            A question deep almost as the mystery of life. --De
                                                  Quincey.
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            O Lord, . . . thy thoughts are very deep. --Ps.
                                                  xcii. 5.
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   5. Of penetrating or far-reaching intellect; not superficial;
      thoroughly skilled; sagacious; cunning.
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            Deep clerks she dumbs.                --Shak.
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   6. Profound; thorough; complete; unmixed; intense; heavy;
      heartfelt; as, deep distress; deep melancholy; deep
      horror. "Deep despair." --Milton. "Deep silence."
      --Milton. "Deep sleep." --Gen. ii. 21. "Deeper darkness."
      --Hoole. "Their deep poverty." --2 Cor. viii. 2.
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            An attitude of deep respect.          --Motley.
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   7. Strongly colored; dark; intense; not light or thin; as,
      deep blue or crimson.
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   8. Of low tone; full-toned; not high or sharp; grave; heavy.
      "The deep thunder." --Byron.
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            The bass of heaven's deep organ.      --Milton.
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   9. Muddy; boggy; sandy; -- said of roads. --Chaucer.
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            The ways in that vale were very deep. --Clarendon.
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   {A deep line of operations} (Military), a long line.

   {Deep mourning} (Costume), mourning complete and strongly
      marked, the garments being not only all black, but also
      composed of lusterless materials and of such fashion as is
      identified with mourning garments.
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