Pertaining to the style and culture of the Gauls in the area of Western Europe including present day France, Luxembourg, Belgium, Switzerland, Northern Italy, and parts of the Netherlands and Germany on the west bank of the Rhine, particularly during the Iron Age and Roman era. For the style and culture of the Gauls under the influence of the Romans, use "Gallo-Roman.

Source: Art & Architecture Thesaurus 

http://vocab.getty.edu/page/aat/300379855