: an opening in a wall, door, etc., that usually contains a sheet of glass
: a sheet of glass that covers an opening in a building, vehicle, etc.
: a large window at the front of a store where goods are displayed so that they can be seen by people who are walking past
Full Definition of WINDOW
a: an opening especially in the wall of a building for admission of light and air that is usually closed by casements or sashes containing transparent material (as glass) and capable of being opened and shut
: a usually narrow interval of time or range of values for which a certain condition or an opportunity exists <coma and multiorgan failure can occur within hours and there may be a very narrow window of opportunity for transplantation—J. P. A. Lodge>—see therapeutic window