roundel
1. a form of rondeau consisting of three stanzas each of three lines with a refrain after the first and the third
2. a small ornamental circular window, panel, medallion, plate, disc, etc.
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
Roundel
1. A small circular panel or window; in glazing, a bull’s-eye or circular light like the bottom of a bottle.

2. A small circular panel or window; an oculus, a bull’s eye, or a circular light like the bottom of a bottle.

See also: French windowIllustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
roundel
1. A small circular panel or window; an
oculus.
2. In glazing, a bull’s-eye or circular light like the bottom of a bottle.
4. In stage lighting, a glass or gelatin color filter used in a
borderlight.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.