1. A window blind or shutter constructed from angled slats.
2. A window made from angled slats of glass.
Etymology: Old French gelosie, jealousy - possibly because such slats allow one to peer through the window without being seen.
Jalousie windows are more common in warmer climates: they provide maximum airflow without obstructing nearby walkways like a casement or awning window might.
One drawback is that they provide little insulation; I've seen them here in Wisconsin, but only on a 3-season sunroom.
The pic is from this company's site.