bull’s-eye
bull’s-eye, 2
1. A figure or ornament of concentric bands.
2. A round or oval aperture, open, louvered, or glazed; an oculus or oeil-de-boeuf
3. The enclosure of such an aperture, a double-arched frame with two or four key voussoirs.
4. A circular aperture in a masonry wall; usually formed by voussoirs or tapered bricks.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.