The American Heritage® Dictionary of the English Language, 4th Edition
n. A horizontal structural member, such as a beam or stone, that spans an opening, as between the uprights of a door or window or between two columns or piers.
n. A horizontal structural beam spanning an opening, such as between the uprights of a door or a window, and which supports the wall above.
the GNU version of the Collaborative International Dictionary of English
n. A horizontal member spanning an opening, and carrying the superincumbent weight by means of its strength in resisting crosswise fracture.
The Century Dictionary and Cyclopedia
n. In architecture, a horizontal piece of timber or stone resting on the jambs of a door or window, or spanning any other open space in a wall or in a columnar construction, and serving to support superincumbent weight.
n. See lingel.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. horizontal beam used as a finishing piece over a door or window
Word Usage
"The word isn't lintel, which is the horizontal top of a doorway."