transom

Concise Oxford English Dictionary © 2008 Oxford University Press:
transom /ˈtrans(ə)m/

▶noun

• 1 the flat surface forming the stern of a boat.

  ■ a horizontal beam reinforcing the stern of a boat.

• 2 a strengthening crossbar, in particular one set above a window or door. Compare with mullion.

• 3 US term for transom window.

– phrases
over the transom N. Amer. informal unsolicited.

– derivatives
transomed adjective.

– origin ME (earlier as traversayn): from OFr. traversin, from traverser (see traverse).