A horizontal bar of wood or stone across a door or window; the crossbar separating a door from the fanlight above it; a window divided by a transom bar.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
1. An intermediate horizontal member of a doorframe, window frame, or similar structure.
2. A horizontal member which separates a door from a window, panel, or louver above.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.