The Collaborative International Dictionary of English v.0.48:

Weatherboarding \Weath"er*board`ing\, n. (Arch.)
   (a) The covering or siding of a building, formed of boards
       lapping over one another, to exclude rain, snow, etc.
   (b) Boards adapted or intended for such use.
       [1913 Webster]

WordNet (r) 3.0 (2006):

weatherboarding
    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, weatherboard, weatherboarding]