A small crenel, used as a decorative design.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
1. A small crenel, whether in an actual battlement or in a decorative design imitating one.
2. A small arrow loop.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.