from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A very slow oscillation, real or apparent, of a satellite as viewed from the larger celestial body around which it revolves.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The act of librating.
- n. 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.
- n. A similar rotational or orbital characteristic of some other celestial body.
from the GNU version of the Collaborative International Dictionary of English
- n. The act or state of librating.
- n. A real or apparent libratory motion, like that of a balance before coming to rest.
from The Century Dictionary and Cyclopedia
- n. The act of librating or balancing, or the state of being balanced; a state of equipoise; balance.
- n. In astronomy, a real or apparent libratory or oscillating motion, like that of a balance before coming to rest.
- n. libration in latitude, in consequenoe of her axis being inclined to the plane of her orbit, so that sometimes one of her poles and sometimes the other declines, as it were, or dips toward the earth
- n. diurnal libration, which is simply a consequence of the lunar parallax. In the last case, an observer at the surface of the earth perceives points near the upper edge of the moon's disk, at the time of her rising, which disappear as her elevation is increased; while new ones on the opposite or lower edge, that were before invisible, come into view as she descends toward the horizon. If the observer were placed at the earth's center he would perceive no diurnal libration.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. (astronomy) a real or apparent slow oscillation of a moon or satellite
Latin lībrātio, lībrātiōn-, oscillation, from lībrātus, past participle of lībrāre, to balance, from lībra, balance.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin lībrātiō ("a hurling, swinging"), from lībrō ("poise, cause to swing"). (Wiktionary)