|1.||the act or an instance of oscillating|
|2.||a real or apparent oscillation of the moon enabling approximately 59 per cent of the surface to be visible from the earth over a period of time|
|[C17: from Latin librātus, from librāre to balance]|
in astronomy, an oscillation, apparent or real, of a satellite, such as the Moon, the surface of which may as a consequence be seen from different angles at different times from one point on its primary body
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