wallboardEnglishOxford New American Dictionarywallboard /ˈwôlbôrd, ˈwɔlbɔrd / ▸ noun mainly North American a type of board made from wood pulp, plaster, or other material, used for covering walls and ceilings: install waterproof wallboard around a shower. ▪ a piece of wallboard: they have chosen wallboards and ceiling sheets in lieu of wood.