The Collaborative International Dictionary of English v.0.48:

Girder \Gird"er\, n. [From Gird to encircle.]
   [1913 Webster]
   1. One who, or that which, girds.
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   2. (Arch. & Engin.) A main beam; a stright, horizontal beam
      to span an opening or carry weight, such as ends of floor
      beams, etc.; hence, a framed or built-up member
      discharging the same office, technically called a compound
      girder. See Illusts. of Frame, and Doubleframed floor,
      under Double.
      [1913 Webster]

   Bowstring girder, Box girder, etc. See under Bowstring,
      Box, etc.

   Girder bridge. See under Bridge.

   Lattice girder, a girder consisting of longitudinal bars
      united by diagonal crossing bars.

   Half-lattice girder, a girder consisting of horizontal
      upper and lower bars connected by a series of diagonal
      bars sloping alternately in opposite directions so as to
      divide the space between the bars into a series of
      triangles. --Knight.

   Sandwich girder, a girder consisting of two parallel wooden
      beams, between which is an iron plate, the whole clamped
      together by iron bolts.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lattice \Lat"tice\, n. [OE. latis, F. lattis lathwork, fr. latte
   lath. See Latten, 1st Lath.]
   1. Any work of wood, metal, plastic, or other solid material,
      made by crossing a series of parallel laths, or thin
      strips, with another series at a diagonal angle, and
      forming a network with openings between the strips; as,
      the lattice of a window; -- called also latticework.
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            The mother of Sisera looked out at a window, and
            cried through the lattice.            --Judg. v. 28.
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   2. (Her.) The representation of a piece of latticework used
      as a bearing, the bands being vertical and horizontal.
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   3. (Crystallography) The arrangement of atoms or molecules in
      a crystal, represented as a repeating arrangement of
      points in space, each point representing the location of
      an atom or molecule; called also crystal lattice and
      space lattice.
      [PJC]

   Lattice bridge, a bridge supported by lattice girders, or
      latticework trusses.

   Lattice girder (Arch.), a girder of which the wed consists
      of diagonal pieces crossing each other in the manner of
      latticework.

   Lattice plant (Bot.), an aquatic plant of Madagascar
      (Ouvirandra fenestralis), whose leaves have interstices
      between their ribs and cross veins, so as to resemble
      latticework. A second species is Ouvirandra Berneriana.
      The genus is merged in Aponogeton by recent authors.
      [1913 Webster]