Overview
Duplication, according to the MWD, is defined as this:
"n: The act of duplicating, or the state of being duplicated; a doubling;"
Disc duplication, however, can take on many other meanings. Purists will point to the process of producing short runs of CDs or DVDs.
Another possible interpretation of the phrase is more conventionally known as disc dupes or dubs. We call these one-off projects simply Disc Copies.
Lastly, if your project will run in the thousands or more, Replication is your area.