Definition of "Window" :

noun: a framework of wood or metal that contains a glass windowpane and is built into a wall or roof to admit light or air

noun: a transparent opening in a vehicle that allow vision out of the sides or back; usually is capable of being opened

noun: a transparent panel (as of an envelope) inserted in an otherwise opaque material

noun: (computer science) a rectangular part of a computer screen that contains a display different from the rest of the screen

noun: an opening in a wall or screen that admits light and air and through which customers can be served

"He stuck his head in the window."

noun: a pane of glass in a window

"The ball shattered the window."

noun: an opening that resembles a window in appearance or function

"He could see them through a window in the trees."

noun: the time period that is considered best for starting or finishing something

"The expanded window will give us time to catch the thieves."