The chapels added to an apse and fanning out in a radial pattern.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
Chapels projecting radially from the curve of an ambulatory or rarely of an apse.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.