- a crosspiece separating a door or the like from a window or fanlight above it.
- Also called transom light, transom window. a window above such a crosspiece.
- a crossbar of wood or stone, dividing a window horizontally.
- a window so divided.
- 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.
- Artillery. a metal piece connecting the sidepieces of the tail or the cheeks of a gun carriage.
1388, transeyn "crossbeam spanning an opening, lintel," probably by dissimilation from L. transtrum "crossbeam" (especially one spanning an opening), from trans- "across" + instrumental suffix -trum. Meaning "small window over a door or other window" is first recorded 1844.
"De Long's cutter was twenty feet, four inches from her bow to her transom stern, with a breadth of six feet at her widest point."
- Hampton Sides, In the Kingdom of Ice: The Grand and Terrible Polar Voyage of the USS Jeannette