n. 1 a an opening in a wall, roof, or vehicle etc., usu. with glass in fixed, sliding, or hinged frames, to admit light or air etc. and allow the occupants to see out. b the glass filling this opening (have broken the window). 2 a space for display behind the front window of a shop. 3 an aperture in a wall etc. through which customers are served in a bank, ticket office, etc. 4 an opportunity to observe or learn. 5 an opening or transparent part in an envelope to show an address. 6 a part of a VDU display selected to show a particular category or part of the data. 7 a an interval during which atmospheric and astronomical circumstances are suitable for the launch of a spacecraft. b any interval or opportunity for action. 8 strips of metal foil dispersed in the air to obstruct radar detection. 9 a range of electromagnetic wavelengths for which a medium is transparent. out of the window colloq. no longer taken into account. window-box a box placed on an outside window-sill for growing flowers. window-cleaner a person who is employed to clean windows. window-dressing 1 the art of arranging a display in a shop-window etc. 2 an adroit presentation of facts etc. to give a deceptively favourable impression. window-ledge = window-sill. window-pane a pane of glass in a window. window-seat 1 a seat below a window, esp. in a bay or alcove. 2 a seat next to a window in an aircraft, train, etc. window-shop (-shopped, -shopping) look at goods displayed in shop-windows, usu. without buying anything. window-shopper a person who window-shops. window-sill a sill below a window. window tax Brit. hist. a tax on windows or similar openings (abolished in 1851). windowed adj. (also in comb.). windowless adj.
[ ME f. ON vindauga (as WIND(1), EYE) ]