a bar of wood or stone across the top of a door or window （门窗上端的）横档，横楣 - (North American English) (also fanlight British and North American English)
a small window above a door or another window （门窗上端的）横档，横楣
Word Originlate Middle English (earlier as traversayn): from Old French traversin, from the verb traverser ‘to cross’.