Polymers with macromolecular chains, that have mostly random orientation with a high entropy, are called amorphous.
This structure allows the chains to move freely, which leads to a high flexibility and elasticity of the material.
Amorphous thermoplastics consist of only 10 % crystalline structures.
Typical amorphous materials are PS, ABS and PC.
This glossary of plastic industry is provided by PLEXPERT Canada Inc.