greenboard
n.β Β«When retiling shower and tub walls, this contractor stands by the outdated practice of using moisture-resistant drywallβcommonly called “greenboard”βas a backer board for tile.Β» ββNot on board with greenboard backer” by Gary Dymski Newsday (Long Island, New York) Oct. 12, 2006. (source: Double-Tongued Dictionary)