There are "official" definitions as noted by Holice, recognized by a formal organization process, and must be known for certification. There are many more informal definitions, which perhaps for your own purpose, as noted, fit the bill. Some of these used and are often seen in other threads here on the QB. Eg. when someone asks what is "modern quilting"? "low volume"? "traditional" etc. And each time, many different interpretations are put forth ... and sometimes those may even conflict among themselves ... and with the "official" ones. Another example, by going to many of the "modern quilt websites" (guilds and otherwise), you will see different interpretations of what a "modern" quilt is.
SallyNeckvatal has presented quite a detailed list of questions. Ones were there is no simple answer, as depending on the reason for the sourcing of the info, we might have different answers.