Yo lo he visto usado para las puertas que tienen varias ventanas/cristales.

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Note added at 15 mins (2008-12-10 07:37:32 GMT)
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En wikipedia encontré una definición (http://en.wikipedia.org/wiki/Door):
A French door, also called a French window, is a door that has multiple windows ("lights") set into it, the full length of the door. Traditional French doors are assembled from individual small pieces of glass and mullions. These doors are also known as true divided lite[sic] French doors. French doors made of double-pane glass (on exterior doors for insulation reasons) may have a decorative grille embedded between the panes, or may also be true divided lite French doors.

Aquí lo vi usado:

http://www.caldoors.com/door/entrada.htm

http://www.ventanasdeseguridad.com/fauser_aluminumdoors.htm

http://images.google.es/imgres?imgurl=http://www.cuisibec.co...

http://www.dimensioncad.com/view.php?g=16&s=1&lang=es




Parece que las dos opciones son correctas, conviene revisar el proz!:

http://www.proz.com/kudoz/english_to_spanish/architecture/10...

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Note added at 20 mins (2008-12-10 07:41:57 GMT)
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Definición:
DEF – A casement window which extends down to the floor often used in pairs.

(casement window) http://en.wikipedia.org/wiki/Casement_window