For most practical purposes, process lens = enlarging lens = macro lens. Ansel Adams comments on the interchangabilty of process and enlarging lenses in his book, The Print.
A “process lens” was intended for use on a large (usually, but not always) horizontal process camera used in the lithographer’s process of converting images into individual cyan, yellow, magenta, and black offset lithography printing plates.
This used to be a photographic process. Now the plates are laser burned into the metal printing plates. Many LF enlarging lens—EL Nikkors in particular up to 360mm—were used on process cameras because in addition to being enlarging lenses, they also performed excellently as process lenses.