- Noun. An opening, usually covered by one or more panes of clear glass, to allow light and air from outside to enter a building or vehicle.
- Noun. An opening, usually covered by glass, in a shop which allows people to view the shop and its products from outside.
- Noun. A period of time when something is available.
- Noun. (GUI) A rectangular area on a computer terminal or screen containing some kind of user interface, displaying the output of and allowing input for one of a number of simultaneously running computer processes.