The Collaborative International Dictionary
Transom \Tran"som\, n. [Probably fr. L. transtrum a crossbeam, transom, from trans across. Cf. Trestle.]
(Arch.) A horizontal crossbar in a window, over a door, or between a door and a window above it. Transom is the horizontal, as mullion is the vertical, bar across an opening. See Illust. of Mullion.
(Naut.) One of the principal transverse timbers of the stern, bolted to the sternpost and giving shape to the stern structure; -- called also transsummer.
(Gun.) The piece of wood or iron connecting the cheeks of some gun carriages.
(Surg.) The vane of a cross-staff.
--Chambers.-
(Railroad) One of the crossbeams connecting the side frames of a truck with each other. Transom knees (Shipbuilding), knees bolted to the transoms and after timbers. Transom window. (Arch.)
A window divided horizontally by a transom or transoms.
A window over a door, with a transom between.
Wiktionary
n. A small hinged window above a door or another window.
WordNet
Usage examples of "transom window".
He looked up at the transom window over the door and saw that there was a light on in the room.
A light showed through the transom window above her door and he knocked softly and waited.
The kitchenette had a high transom window cut through to the hall, presumably for ventilation, and it would be easily accessible from the top of the refrigerator, but it was closed and latched.
A shaft of sunlight through the transom window above the door blazed like fire in her short red hair.
Lightning flashed and showed through the shuttered windows and the glass transom window over the door.