1) Board 2) Hardboard 3) Plank 1) Chbd 2) Hardboard 
cheap cardboard or paperboard used as backing for photographs or in making cartons and boxes where strength and appearance are not essential. ...
Inexpensive, single-ply cardboard, usually brown or gray.
[n] - a cheap hard material made from wood chips that are pressed together and bound with synthetic resin
A board made from waste paper used mainly in packaging, especially with a white liner and coating, but also for making the covers of case books.
hardboard noun a cheap hard material made from wood chips that are pressed together and bound with synthetic resin
a low grade of cardboard, used as a backing for pads of paper, a stiffener for photographs in mailing, etc. · a thin, stiff sheet material made from wastepaper. · a type of board made from compressed waste wood bound together with synthetic resin.