Any of the sloping roofs at the side of a real tennis court.
An outhouse or other structure (especially one with a sloping roof) attached to the outside wall of a building, sometimes as protection from the weather.
An apartment or suite found on an upper floor, or floors, of a tall building, especially one that is expensive or luxurious with panoramic views. Sometimes these are located just under "penthouse mechanical" floors.
To provide with a penthouse, shelter by means of a shed sloping from a wall, or anything similar.