transom

UK: /ˈtrænsəm/ US: /ˈtrænsəm/ ,(tran′səm)

WordReference Random House Learner's Dictionary of American English © 2025

tran•som /ˈtrænsəm/   n. [countable]

1. Building a crosspiece separating a door or window from a window above it.
2. Building a window above such a crosspiece.

WordReference Random House Unabridged Dictionary of American English © 2025

tran•som  (tran′səm), n. 

1. a crosspiece separating a door or the like from a window or fanlight above it.
2. Also called tran′som light′, transom window. a window above such a crosspiece.
3. a crossbar of wood or stone, dividing a window horizontally.
4. a window so divided.
5. [Naut.]
   • a flat termination to a stern, above the water line.
   • framework running athwartships in way of the sternpost of a steel or iron vessel, used as a support for the frames of the counter.
6. [Artillery.] a metal piece connecting the sidepieces of the tail or the cheeks of a gun carriage.

• Old French traversin crosspiece, derivative of travers breadth; see traverse
• late Middle English traunsum, traunsom, Middle English transyn, probably alteration (by association with trans-) of traversayn 1325–75

tran ′somed, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

transom / ˈtrænsəm/ noun

1. a horizontal member across a window
   Compare mullion
2. a horizontal member that separates a door from a window over it
3. the usual US name for fanlight
4. a surface forming the stern of a vessel, either vertical or canted either forwards (reverse transom) or aft at the upper side
5. any of several transverse beams used for strengthening the stern of a vessel

Etymology: 14th Century: earlier traversayn, from Old French traversin, from traverse

ˈtransomed adjective