In the Star Wars universe, a repulsorlift engine (often just called a "repulsor") is a device capable of negating the effects of gravity. The technology is commonly used on vehicles ranging from landspeeders to starships.
Repulsorlifts exist in a variety of sizes, from shipboard systems capable of supporting mile-long spacecraft to the miniature versions built into certain droids. They require a gravity well to operate, limiting their use to the immediate vicinity of planets or other massive objects. Unlike chemical thrusters, repulsorlifts do not seem to adversely affect whatever is located underneath them. Their quiet operation and low power requirements makes them suitable for use in densely populated areas. Their popularity and widespread use indicate high reliability.