Wikipedia
The Moonbus is a fictitious transportation vehicle which appears in the film 2001: A Space Odyssey. The word “moonbus” isn't referred to explicitly in the film itself; rather, it's called a “rocket bus” in dialogue, and, in an early draft of the screenplay, is described as a “moon rocket bus”.
A moonbus is a vehicle for transporting cargo and personnel across the surface of the Moon. Its mode of operation is to maintain a fixed cruising altitude by sustained downward thrust from a battery of rocket motors, exactly balancing the Moon's force of gravity. Horizontal motion is imparted by brief horizontal bursts of thrust. The Moon is airless. In the absence of aerodynamic drag, the vehicle continues to travel unimpeded as long as altitude above geographical obstacles is maintained.
In reality this scheme is possible, but also wasteful. Due to the Oberth effect, the more efficient use of propellant is to hurl the craft on a ballistic trajectory which intersects the lunar surface at the departure and destination points. Thrust would be exerted only during a boost phase at departure, and during approach to destination for a soft landing.