Source : Webster's Revised Unabridged Dictionary (1913)

Weatherboard \Weath"er*board`\, n.
   1. (Naut.)
      (a) That side of a vessel which is toward the wind; the
          windward side.
      (b) A piece of plank placed in a porthole, or other
          opening, to keep out water.

   2.
      (a) (Arch.) A board extending from the ridge to the eaves
          along the slope of the gable, and forming a close
          junction between the shingling of a roof and the side
          of the building beneath.
      (b) A clapboard or feather-edged board used in
          weatherboarding.

Source : WordNet®

weatherboard
     n 1: a long thin board with one edge thicker than the other; used
          as siding by lapping one board over the board below
          [syn: {clapboard}, {weatherboarding}]
     2: the side toward the wind [syn: {to windward}, {windward side},
         {weather side}]