noun

transom

TRAN-sum/ˈtrænsəm/

A horizontal bar dividing an opening.

A wooden transom divides the door opening into two unequal sections.

Front view of plain wooden door with small rectangular glass transom directly above it; horizontal separating bar clear, only doorway structure on white.

Etymology

transomMiddle Englishcrossbeam spanning an opening

Middle English transeyn named a crossbeam spanning an opening. The term came to name the bar separating a door from the window above it, then the window itself.

In context

Decor Hunter2:15

… six consider a glass front door this narrow entryway lets in plenty of light via the glass paneled front door and transom window

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More examples

The upper pane rests on a narrow transom.
We paint the transom to match the window frame.
Both windows have stone transoms midway up their frames.

Forms

transom · transoms

Similar words

crossbar: Any horizontal bar across a structure, not specifically an opening.
crosspiece: A piece set across others, not necessarily dividing an opening.