Hohmann transfer

Etymology
Named after, the German engineer who described it.

Noun

 * 1)  An elliptical orbit used to transfer a spacecraft between two circular orbits of different altitudes in the same plane, with the periapsis of the orbit being tangent to the smaller circular orbit and its apoapsis being tangent to the larger circular orbit.
 * 2)  The process of using such an orbit to transfer between two other orbits.