| 1. | Chiefly Northeastern U.S. a long, thin board, thicker along one edge than the other, used in covering the outer walls of buildings, being laid horizontally, the thick edge of each board overlapping the thin edge of the board below it. |
| 2. | British. a size of oak board used for making barrel staves and for wainscoting. |
| 3. | of or made of clapboard: a clapboard house. |