noun

• (architecture) A crosspiece over a door; a lintel.
• (architecture) A horizontal glazing bar in a window.
• A transom window.
• (nautical) Any of several transverse structural members in a ship, especially at the stern; a thwart.
• (nautical) The flat or nearly flat stern of a boat or ship.
• The horizontal beam on a cross or gallows.
• (figuratively, usually attributively) Items that have arrived over the transom.