from
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]