broach
1. In quarrying, to free stone blocks from the ledge by cutting out the webbing between holes drilled close together in a row.
2. To finish a stone surface with broad diagonal parallel grooves cut by a pointed chisel.
3. A half pyramid above the corners of a square tower to provide a transition to an octagonal spire.
4. A spire sometimes springing from a tower without an intermediate parapet.
5. Any pointed ornamental structure.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.