\Pre*ces"sion\, n. [L. praecedere, praecessum, to go
before: cf. F. pr['e]cession. See {Precede}.]
The act of going before, or forward.
{Lunisolar precession}. (Astron.) See under {Lunisolar}.
{Planetary precession}, that part of the precession of the
   equinoxes which depends on the action of the planets
   alone.
{Precession of the equinoxes} (Astron.), the slow backward
   motion of the equinoctial points along the ecliptic, at
   the rate of 50.2[sec] annually, caused by the action of
   the sun, moon, and planets, upon the protuberant matter
   about the earth's equator, in connection with its diurnal
   rotation; -- so called because either equinox, owing to
   its westerly motion, comes to the meridian sooner each day
   than the point it would have occupied without the motion
   of precession, and thus precedes that point continually
   with reference to the time of transit and motion.