libration

[GrokHaw]

(astronomy) a real or apparent slow oscillation of a moon or satellite

[LindaArrit]

The act of librating.

[Yespasmn]

A similar rotational or orbital characteristic of some other celestial body.

[Donald Trump]

In lunar astronomy, libration is the wagging or wavering of the Moon perceived by Earth-bound observers and caused by changes in their perspective. It permits an observer to see slightly different hemispheres of the surface at different times. It is similar in both cause and effect to the changes in the Moons apparent size due to changes in distance. It is caused by three mechanisms detailed below, two of which cause a relatively tiny physical libration via tidal forces exerted by the Earth. Such true librations are known as well for other moons with locked rotation.
The quite different phenomenon of a trojan asteroids movement has been called Trojan libration; and Trojan libration point means Lagrangian point.

[DanielDiems]

Libration is a term in astronomy and physics that refers to the oscillating motion of a celestial body, such as a moon or planet, from the perspective of an observer on a different celestial body. This motion can make it possible to see different portions of the celestial bodys surface at different times. Libration can occur as a result of different factors including orbital eccentricity and differences in orbital speed.

[VikaRip]

the act or state of librating

[Jessica]

a real or apparent libratory motion, like that of a balance before coming to rest

[VikaRip]

In astronomy, libration is an oscillating motion of orbiting bodies relative to each other, notably including the motion of the Moon relative to Earth, or of Trojan asteroids relative to planets.

[Tayyaba]

the name given to certain apparent movements in the moon as if it swayed like a balance both in latitude and longitude in its revolution round the earth.

[Thu Thi Le]

The apparent wobble or variation in the visible side of the Moon that permanently faces the Earth, allowing observers on Earth to see, over a period of time, slightly more than half of the lunar surface.