Gacchadipati means the head or supreme leader of a Jain gaccha — that is, a monastic order/group, especially in the Śvetāmbara tradition. In simple words, it is the chief Acharya or administrative head of that gaccha. ( jainpedia.org)

In Jain usage, gaccha refers to a monastic order or group of monks, and gacchadipati is the person who leads that order. ( jainpedia.org)