Meaning

noun (trademark) an operating system with a graphical user interface

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

originFrom windows, in reference to the user-interface display elements.

Etymology from Wiktionary, CC BY-SA 3.0