Dymondwood is an engineered wood/plastic composite. It has the appearance of wood, but the stability (resisting shrinking, expanding and cracking) of a composite. It is similar to plywood, in that it consists of sheets of (birch?) veneer which are then placed in a vacuum that is flooded with colored resin. The sheets are then stacked and placed under heat and pressure, which fuses them together. The color of the resin is matched to whatever wood is being emulated, though a top layer(s) of the actual wood can be used to more fully duplicate a given wood.
While Dymondwood is a specific brand, there are other similar materials such as WebbWood, ColorWood, Spectraply & Dymalux. It is similar to the Pakkawood used on the Knife Center exclusives.