Furring

Part of speech: noun (n.)

1. The leveling of a surface, or the preparing of an air space, by means of strips of board or of larger pieces. See Fur, v. t., 3.

2. The strips thus laid on.

3. Double planking of a ship's side.

4. A deposit from water, as on the inside of a boiler; also, the operation of cleaning away this deposit.