Additive Manufacturing (AM), also known as Direct Digital Manufacturing, is the process of joining materials, such as liquid resin, powders to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies. Synonyms: additive fabrication, additive processes, additive techniques, additive layer manufacturing, layer manufacturing, freeform fabrication.
Source: ASTM International F42 Committee on Additive Manufacturing Technologies