The Collaborative International Dictionary of English v.0.48:

Grid \Grid\ (gr[i^]d), n.
   1. A grating of thin parallel bars, similar to a gridiron.
      [1913 Webster]

   2. (Elec.) A plate or sheet of lead with perforations, or
      other irregularities of surface, by which the active
      material of a secondary battery or accumulator is
      supported.
      [Webster 1913 Suppl.]

   3. (Electronics) a mesh or coil of fine wire in an electron
      tube, connected to the circuit so as to regulate the
      current passing through the tube.
      [PJC]

   4. any network of crossing horizontal and vertical lines; --
      they are used, for example, as reference coordinates to
      locate objects or places on a map.
      [PJC]

   5. anything resembling a grid[4], as the Manhattan street
      grid. See also gridlock.
      [PJC]

   6. a network of connected conductors for distributing
      electrical power, especially one using high-tension lines
      for wide geographic distribution of power; as, the
      Northeast power grid.
      [PJC]

   7. (Football) the gridiron.
      [PJC]

WordNet (r) 3.0 (2006):

grid
    n 1: a pattern of regularly spaced horizontal and vertical lines
    2: a system of high tension cables by which electrical power is
       distributed throughout a region [syn: power system, power
       grid, grid]
    3: a perforated or corrugated metal plate used in a storage
       battery as a conductor and support for the active material
       [syn: grid, storage-battery grid]
    4: an electrode placed between the cathode and anode of a vacuum
       tube to control the flow of electrons through the tube [syn:
       grid, control grid]
    5: a cooking utensil of parallel metal bars; used to grill fish
       or meat [syn: grid, gridiron]