librate

Etymology 1

From Medieval Latin lībrāta, from Latin lībra (“pound”).

noun

1. (now historical) A piece of land having a value of one pound per year.

Etymology 2

From the participle stem of Latin lībrāre, from lībra (“a balance”).

verb

1. (intransitive) To oscillate (like the beam of a balance).
   The currently observed orbital resonances at the 2:1 mean motion commensurabilities involving Io-Europa and Europa-Ganymede are such that the resonance variables θ₁=λ₁-2λ₂+ω₁ and θ₃=λ₂-2λ₃+ω₂ librate about 0° and θ₂=λ₁-2λ₂+ω₂ librates about 180°, all with small amplitude. 2002-10-18, S. J. Peale, Man Hoi Lee, “A Primordial Origin of the Laplace Relation Among the Galilean Satellites”, in Science, volume 298, number 5593, →DOI, page 594
   Their parts all librate on too nice a beam. 1796, William Cliffton, The Group
2. (intransitive) To be poised; to balance oneself.
   Her playful Sea-horse […] His watery way with waving volutes wins, / Or listening librates on unmoving fins. 1791, Erasmus Darwin, The Economy of Vegetation, J. Johnson, page 138
3. (obsolete, transitive) To place in a balance; to weigh.