Source : Webster's Revised Unabridged Dictionary (1913)

Lath \Lath\, n.; pl. {Laths}. [OE. laththe, latthe, latte, AS.
   l[ae]tta; akin to D. lat, G. latte, OHG. latta; cf. W. llath
   a rod, staff, yard. Cf. {Lattice}, {Latten}.]
   A thin, narrow strip of wood, nailed to the rafters, studs,
   or floor beams of a building, for the purpose of supporting
   the tiles, plastering, etc. A corrugated metallic strip or
   plate is sometimes used.

   {Lath brick}, a long, slender brick, used in making the floor
      on which malt is placed in the drying kiln.

   {Lath nail} a slender nail for fastening laths.

Lath \Lath\, v. t. [imp. & p. p. {Lathed}; p. pr. & vb. n.
   {Lathing}.]
   To cover or line with laths.

Source : WordNet®

lath
     n : a narrow thin strip of wood used as backing for plaster or
         to make latticework