thin board consisting of a core of plaster of Paris covered with heavy paper, used in wide sheets as a base or substitute for plaster in walls, partitions, etc.
See plasterboard in American Heritage Dictionary 4
(plăsˈtər-bôrdˌ, -bōrdˌ)
noun
A rigid board made of layers of fiberboard or paper bonded to a gypsum plaster core, used instead of plaster or wood panels in construction to form walls. Also called gypsum board, wallboard.