ABS - acrylonitrile butadiene styrene
ABS is an amorphous thermoplastic blend. The recipe is 15-35% acrylnitrile, 5-30% butadiene and 40-60% styrene. Depending on the blend different properties can be achieved.
Acrylnitrile contributes with thermal and chemical resistence, and the rubberlike butadiene gives ductility and impact strength. Styrene gives the glossy surface and makes the material easily machinable and less expensive.
Generally, ABS has good impact strength also at low temperatures. It has satisfactory stiffness and dimensional stability, glossy surface and is easy to machine. If UV-stabilizators are added, ABS is suitable for outdoor applications.
Above information cited from: http://www.designinsite.dk/htmsider/m0007.htm
More information of ABS on Wikipedia: http://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene