Source : Webster's Revised Unabridged Dictionary (1913)

Equilibrium \E`qui*lib"ri*um\, n.; pl. E. {Equilibriums}, L.
   {Equilibria}. [L. aequilibrium, fr. aequilibris in
   equilibrium, level; aequus equal + libra balance. See
   {Equal}, and {Librate}.]
   1. Equality of weight or force; an equipoise or a state of
      rest produced by the mutual counteraction of two or more
      forces.

   2. A level position; a just poise or balance in respect to an
      object, so that it remains firm; equipoise; as, to
      preserve the equilibrium of the body.

            Health consists in the equilibrium between those two
            powers.                               --Arbuthnot.

   3. A balancing of the mind between motives or reasons, with
      consequent indecision and doubt.

   {Equilibrium valve} (Steam Engine), a balanced valve. See
      under {Valve}.