The highest point.
The point, in any trajectory of an object in space, where it is farthest from the Earth.
The point, in an orbit about the Earth, that is farthest from the Earth: the apoapsis of an Earth orbiter.
The point, in an orbit about any planet, that is farthest from the planet: the apoapsis of any satellite.
The top external level of a building.
The external covering at the top of a building.
The upper part of a cavity.
An overhanging rock wall.
The surface or bed of rock immediately overlying a bed of coal or a flat vein.
To cover or furnish with a roof.
To traverse buildings by walking or climbing across their roofs.
To put into prison, to bird.
To shelter as if under a roof.