The Collaborative International Dictionary of English v.0.48:

Dead \Dead\ (d[e^]d), a. [OE. ded, dead, deed, AS. de['a]d; akin
   to OS. d[=o]d, D. dood, G. todt, tot, Icel. dau[eth]r, Sw. &
   Dan. d["o]d, Goth. daubs; prop. p. p. of an old verb meaning
   to die. See Die, and cf. Death.]
   1. Deprived of life; -- opposed to alive and living;
      reduced to that state of a being in which the organs of
      motion and life have irrevocably ceased to perform their
      functions; as, a dead tree; a dead man. "The queen, my
      lord, is dead." --Shak.
      [1913 Webster]

            The crew, all except himself, were dead of hunger.
                                                  --Arbuthnot.
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            Seek him with candle, bring him dead or living.
                                                  --Shak.
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   2. Destitute of life; inanimate; as, dead matter.
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   3. Resembling death in appearance or quality; without show of
      life; deathlike; as, a dead sleep.
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   4. Still as death; motionless; inactive; useless; as, dead
      calm; a dead load or weight.
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   5. So constructed as not to transmit sound; soundless; as, a
      dead floor.
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   6. Unproductive; bringing no gain; unprofitable; as, dead
      capital; dead stock in trade.
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   7. Lacking spirit; dull; lusterless; cheerless; as, dead eye;
      dead fire; dead color, etc.
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   8. Monotonous or unvaried; as, a dead level or pain; a dead
      wall. "The ground is a dead flat." --C. Reade.
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   9. Sure as death; unerring; fixed; complete; as, a dead shot;
      a dead certainty.
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            I had them a dead bargain.            --Goldsmith.
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   10. Bringing death; deadly. --Shak.
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   11. Wanting in religious spirit and vitality; as, dead faith;
       dead works. "Dead in trespasses." --Eph. ii. 1.
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   12. (Paint.)
       (a) Flat; without gloss; -- said of painting which has
           been applied purposely to have this effect.
       (b) Not brilliant; not rich; thus, brown is a dead color,
           as compared with crimson.
           [1913 Webster]

   13. (Law) Cut off from the rights of a citizen; deprived of
       the power of enjoying the rights of property; as, one
       banished or becoming a monk is civilly dead.
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   14. (Mach.) Not imparting motion or power; as, the dead
       spindle of a lathe, etc. See Spindle.
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   15. (Elec.) Carrying no current, or producing no useful
       effect; -- said of a conductor in a dynamo or motor, also
       of a telegraph wire which has no instrument attached and,
       therefore, is not in use.
       [Webster 1913 Suppl.]

   16. Out of play; regarded as out of the game; -- said of a
       ball, a piece, or a player under certain conditions in
       cricket, baseball, checkers, and some other games.

             [In golf], a ball is said to lie dead when it lies
             so near the hole that the player is certain to hole
             it in the next stroke.               --Encyc. of
                                                  Sport.
       [Webster 1913 Suppl.]

   Dead ahead (Naut.), directly ahead; -- said of a ship or
      any object, esp. of the wind when blowing from that point
      toward which a vessel would go.

   Dead angle (Mil.), an angle or space which can not be seen
      or defended from behind the parapet.

   Dead block, either of two wooden or iron blocks intended to
      serve instead of buffers at the end of a freight car.

   Dead calm (Naut.), no wind at all.

   Dead center, or Dead point (Mach.), either of two points
      in the orbit of a crank, at which the crank and connecting
      rod lie a straight line. It corresponds to the end of a
      stroke; as, A and B are dead centers of the crank
      mechanism in which the crank C drives, or is driven by,
      the lever L.

   Dead color (Paint.), a color which has no gloss upon it.

   Dead coloring (Oil paint.), the layer of colors, the
      preparation for what is to follow. In modern painting this
      is usually in monochrome.

   Dead door (Shipbuilding), a storm shutter fitted to the
      outside of the quarter-gallery door.

   Dead flat (Naut.), the widest or midship frame.

   Dead freight (Mar. Law), a sum of money paid by a person
      who charters a whole vessel but fails to make out a full
      cargo. The payment is made for the unoccupied capacity.
      --Abbott.

   Dead ground (Mining), the portion of a vein in which there
      is no ore.

   Dead hand, a hand that can not alienate, as of a person
      civilly dead. "Serfs held in dead hand." --Morley. See
      Mortmain.

   Dead head (Naut.), a rough block of wood used as an anchor
      buoy.

   Dead heat, a heat or course between two or more race
      horses, boats, etc., in which they come out exactly equal,
      so that neither wins.

   Dead horse, an expression applied to a debt for wages paid
      in advance. [Law]

   Dead language, a language which is no longer spoken or in
      common use by a people, and is known only in writings, as
      the Hebrew, Greek, and Latin.

   Dead plate (Mach.), a solid covering over a part of a fire
      grate, to prevent the entrance of air through that part.


   Dead pledge, a mortgage. See Mortgage.

   Dead point. (Mach.) See Dead center.

   Dead reckoning (Naut.), the method of determining the place
      of a ship from a record kept of the courses sailed as
      given by compass, and the distance made on each course as
      found by log, with allowance for leeway, etc., without the
      aid of celestial observations.

   Dead rise, the transverse upward curvature of a vessel's
      floor.

   Dead rising, an elliptical line drawn on the sheer plan to
      determine the sweep of the floorheads throughout the
      ship's length.

   Dead-Sea apple. See under Apple.

   Dead set. See under Set.

   Dead shot.
       (a) An unerring marksman.
       (b) A shot certain to be made.

   Dead smooth, the finest cut made; -- said of files.

   Dead wall (Arch.), a blank wall unbroken by windows or
      other openings.

   Dead water (Naut.), the eddy water closing in under a
      ship's stern when sailing.

   Dead weight.
       (a) A heavy or oppressive burden. --Dryden.
       (b) (Shipping) A ship's lading, when it consists of heavy
           goods; or, the heaviest part of a ship's cargo.
       (c) (Railroad) The weight of rolling stock, the live
           weight being the load. --Knight.

   Dead wind (Naut.), a wind directly ahead, or opposed to the
      ship's course.

   To be dead, to die. [Obs.]
      [1913 Webster]

            I deme thee, thou must algate be dead. --Chaucer.

   Syn: Inanimate; deceased; extinct. See Lifeless.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

center \cen"ter\ (s[e^]n"t[~e]r), n. [F. centre, fr. L. centrum,
   fr. Gr. ke`ntron any sharp point, the point round which a
   circle is described, fr. kentei^n to prick, goad.]
   1. A point equally distant from the extremities of a line,
      figure, or body, or from all parts of the circumference of
      a circle; the middle point or place.
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   2. The middle or central portion of anything.
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   3. A principal or important point of concentration; the
      nucleus around which things are gathered or to which they
      tend; an object of attention, action, or force; as, a
      center of attaction.
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   4. The earth. [Obs.] --Shak.
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   5. Those members of a legislative assembly (as in France) who
      support the existing government. They sit in the middle of
      the legislative chamber, opposite the presiding officer,
      between the conservatives or monarchists, who sit on the
      right of the speaker, and the radicals or advanced
      republicans who occupy the seats on his left, See Right,
      and Left.
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   6. (Arch.) A temporary structure upon which the materials of
      a vault or arch are supported in position until the work
      becomes self-supporting.
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   7. (Mech.)
      (a) One of the two conical steel pins, in a lathe, etc.,
          upon which the work is held, and about which it
          revolves.
      (b) A conical recess, or indentation, in the end of a
          shaft or other work, to receive the point of a center,
          on which the work can turn, as in a lathe.
          [1913 Webster]

   Note: In a lathe the

   live center is in the spindle of the head stock; the

   dead center is on the tail stock.

   Planer centers are stocks carrying centers, when the object
      to be planed must be turned on its axis.
      [1913 Webster]

   Center of an army, the body or troops occupying the place
      in the line between the wings.

   Center of a curve or Center of a surface (Geom.)
      (a) A point such that every line drawn through the point
          and terminated by the curve or surface is bisected at
          the point.
      (b) The fixed point of reference in polar coordinates. See
          Coordinates.

   Center of curvature of a curve (Geom.), the center of that
      circle which has at any given point of the curve closer
      contact with the curve than has any other circle whatever.
      See Circle.

   Center of a fleet, the division or column between the van
      and rear, or between the weather division and the lee.

   Center of gravity (Mech.), that point of a body about which
      all its parts can be balanced, or which being supported,
      the whole body will remain at rest, though acted upon by
      gravity.

   Center of gyration (Mech.), that point in a rotating body
      at which the whole mass might be concentrated
      (theoretically) without altering the resistance of the
      intertia of the body to angular acceleration or
      retardation.

   Center of inertia (Mech.), the center of gravity of a body
      or system of bodies.

   Center of motion, the point which remains at rest, while
      all the other parts of a body move round it.

   Center of oscillation, the point at which, if the whole
      matter of a suspended body were collected, the time of
      oscillation would be the same as it is in the actual form
      and state of the body.

   Center of percussion, that point in a body moving about a
      fixed axis at which it may strike an obstacle without
      communicating a shock to the axis.

   Center of pressure (Hydros.), that point in a surface
      pressed by a fluid, at which, if a force equal to the
      whole pressure and in the same line be applied in a
      contrary direction, it will balance or counteract the
      whole pressure of the fluid.
      [1913 Webster] Center

WordNet (r) 3.0 (2006):

dead center
    n 1: the position of a crank when it is in line with the
         connecting rod and not exerting torque [syn: dead center,
         dead centre]