The Collaborative International Dictionary of English v.0.48:

Libration point \Li*bra"tion point`\ (l[-i]*br[=a]"sh[u^]n
   point`), n.
   any one of five points in the plane of a system of two large
   astronomical bodies orbiting each other, as the Earth-moon
   system, where the gravitational pull of the two bodies on an
   object are approximately equal, and in opposite directions. A
   solid object moving in the same velocity and direction as
   such a libration point will remain in gravitational
   equilibrium with the two bodies of the system and not fall
   toward either body.
   [1913 Webster]