clapboardn.1. A narrow board, thicker at one edge than at the other; -- used for weatherboarding the outside of houses.()2. A stave for a cask.(Halliwell.)v. t. To cover with clapboards; as, to clapboard the sides of a house.(Bartlett.)n. Oatmeal cake or bread clapped or beaten till it is thin.(Halliwell.)