libration

  1. Noun.  The act of librating.
  2. Noun.  (astronomy) 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.
  3. Noun.  (context, by extension) A similar rotational or orbital characteristic of some other celestial body.

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This entry was last updated on RefTopia from its source on 3/20/2012.