Infinite glider
An infinite gilder, sometimes abbreviated as infiniglider, is a glider which abuses a glitch in KSP's aerodynamics and allows a craft to accelerate indefinitely without an engine. Most infinite glider designs use many control surfaces which are flapped very rapidly. It is possible to use infinite gliders on every celestial body with an atmosphere.
Mechanics
Infinite gliders work by exploiting the aerodynamics system and the way in which control surfaces interact with the atmosphere. When a light craft is equipped with several, rapidly moving them back and forth causes the airplane to quickly wobble in alternating directions and accelerate, possibly to speeds in excess of several kilometers a second. However, infinite gliders tend to experience high g-forces and physics bugs due to the erratic and rapidly changing nature of their acceleration, and can tear apart if flown too quickly.
Infinite gliders resemble real-life ornithopters.