Definitions 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 the wall of a building (usually to admit light and air)

  Example: "He stuck his head in the window"

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

  Example: "He could see them through a window in the trees"

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

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

• noun:   a pane in a window

  Example: "The ball shattered the window"