\Ac*cel`er*a"tion\, n. [L. acceleratio: cf. F.
acc['e]l['e]ration.]
The act of accelerating, or the state of being accelerated;
increase of motion or action; as, a falling body moves toward
the earth with an acceleration of velocity; -- opposed to
{retardation}.
      A period of social improvement, or of intellectual
      advancement, contains within itself a principle of
      acceleration.                            --I. Taylor.
(Astr. & Physics.)
{Acceleration of the moon}, the increase of the moon's mean
   motion in its orbit, in consequence of which its period of
   revolution is now shorter than in ancient times.
{Acceleration} and {retardation of the tides}. See {Priming
   of the tides}, under {Priming}.
{Diurnal acceleration of the fixed stars}, the amount by
   which their apparent diurnal motion exceeds that of the
   sun, in consequence of which they daily come to the
   meridian of any place about three minutes fifty-six
   seconds of solar time earlier than on the day preceding.
{Acceleration of the planets}, the increasing velocity of
   their motion, in proceeding from the apogee to the perigee
   of their orbits.