This seems like a definition people on both sides could accept:
The issues I am describing here all go back to how one views the Bible. Is it the divine revelation of God’s will for mankind? Or is it just the product of human religious instincts, a collection of writings cobbled together as ancient people fought to establish their views? The way one answers these questions creates something of a divide in the field of early Christian studies. Though the terminology is imperfect, we can, generally speaking, distinguish between scholars who are “liberal” and “conservative.” These terms do not describe a political outlook. Rather, they categorize two approaches to the Bible that are not easy to describe with any other terminology.
A biblical conservative understands the Old and New Testaments to be authored by people who were inspired by God Himself, which means that whatever is recorded in Scripture must be true and accurate in a meaningful sense. A liberal, in contrast, considers the biblical writings as important historical documents, though written by human hands only, and therefore prone to errors or even falsifications.
Taken from Bryan M. Liftin’s After Acts: Exploring the Lives and Legends of the Apostles. Moody, 2015, 199 pages. See p. 17-18.