Available Definitions:
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. See Illust . of Mullion.
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.