1. (n.) 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.
2. (n.) One of the principal transverse timbers of the stern, bolted to the sternpost and giving shape to the stern structure; -- called also transsummer.
3. (n.) The piece of wood or iron connecting the cheeks of some gun carriages.
4. (n.) The vane of a cross-staff.
5. (n.) One of the crossbeams connecting the side frames of a truck with each other.
Thesaurus Entries
air duct, air hole, air passage, air shaft, air tube, airway, bay, bay window, blowhole, bow window, breathing hole, casement, casement window, cross bitt, crossarm, crossbar, crosspiece, doubletree, fan window, fanlight, grille, lancet window, lantern, lattice, light, louver, louver window, louverwork, naris, nostril, oriel, pane, picture window, port, porthole, rose window, shaft, singletree, skylight, spilehole, spiracle, swingletree, touchhole, transept, transversal, transverse, traverse, vent, ventage, venthole, ventiduct, ventilating shaft, ventilator, whippletree, wicket, wind tunnel, window, window bay, window glass, windowpane
