The Collaborative International Dictionary of English v.0.48:

Graving \Grav"ing\, n. [From Grave to clean.]
   The act of cleaning a ship's bottom.
   [1913 Webster]

   Graving dock. (Naut.) See under Dock.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dock \Dock\, n. [Akin to D. dok; of uncertain origin; cf. LL.
   doga ditch, L. doga ditch, L. doga sort of vessel, Gr. ?
   receptacle, fr. ? to receive.]
   1. An artificial basin or an inclosure in connection with a
      harbor or river, -- used for the reception of vessels, and
      provided with gates for keeping in or shutting out the
      tide.
      [1913 Webster]

   2. The slip or water way extending between two piers or
      projecting wharves, for the reception of ships; --
      sometimes including the piers themselves; as, to be down
      on the dock.
      [1913 Webster]

   3. The place in court where a criminal or accused person
      stands.
      [1913 Webster]

   Balance dock, a kind of floating dock which is kept level
      by pumping water out of, or letting it into, the
      compartments of side chambers.

   Dry dock, a dock from which the water may be shut or pumped
      out, especially, one in the form of a chamber having walls
      and floor, often of masonry and communicating with deep
      water, but having appliances for excluding it; -- used in
      constructing or repairing ships. The name includes
      structures used for the examination, repairing, or
      building of vessels, as graving docks, floating docks,
      hydraulic docks, etc.

   Floating dock, a dock which is made to become buoyant, and,
      by floating, to lift a vessel out of water.

   Graving dock, a dock for holding a ship for graving or
      cleaning the bottom, etc.

   Hydraulic dock, a dock in which a vessel is raised clear of
      the water by hydraulic presses.

   Naval dock, a dock connected with which are naval stores,
      materials, and all conveniences for the construction and
      repair of ships.

   Sectional dock, a form of floating dock made in separate
      sections or caissons.

   Slip dock, a dock having a sloping floor that extends from
      deep water to above high-water mark, and upon which is a
      railway on which runs a cradle carrying the ship.

   Wet dock, a dock where the water is shut in, and kept at a
      given level, to facilitate the loading and unloading of
      ships; -- also sometimes used as a place of safety; a
      basin.
      [1913 Webster]

WordNet (r) 3.0 (2006):

graving dock
    n 1: a large dock from which water can be pumped out; used for
         building ships or for repairing a ship below its waterline
         [syn: dry dock, drydock, graving dock]