Source : Webster's Revised Unabridged Dictionary (1913)

Librate \Li"brate\ (l[imac]"br[=a]t), v. i. [imp. & p. p.
   {Librated} (l[imac]"br[asl]*t[e^]d); p. pr. & vb. n.
   {Librating}.] [L. libratus, p. p. of librare to balance, to
   make even, fr. libra. Cf. {Level}, {Deliberate},
   {Equilibrium}.]
   To vibrate as a balance does before resting in equilibrium;
   hence, to be poised.

         Their parts all librate on too nice a beam. --Clifton.