What does AMBUL stand for?

Ambulatory

1.Passageways surrounding the central part of the choir, which is often a continuation of the side aisles . The most common design of the Gothic era was the double ambulatory surrounded by semi-circular radiating chapels such as at the Abbey Church of Saint-Denis.2.A semicircular or polygonal passageway around the apse of a church. 3.continuation of the aisles of the choir around the apse, sometimes giving access to smaller chapels