A manufactured wood panel made of 1- to 2-inch wood chips and glue, often used as a substitute for plywood in exterior walls and roof sheathing. Also called chipboard, flakeboard and waferboard.
oriented strand board (Wikipedia)
Oriented strand board (OSB), also known as flakeboard, sterling board and aspenite in British English, is a type of engineered wood similar to particle board, formed by adding adhesives and then compressing layers of wood strands (flakes) in specific orientations. It was invented by Armin Elmendorf in California in 1963. OSB may have a rough and variegated surface with the individual strips of around 2.5 cm × 15 cm (1.0 by 5.9 inches), lying unevenly across each other and comes in a variety of types and thicknesses.