Precession

noun

1. Precedence.

   "But as it will not do to talk entirely at random, as Montaigne does, and Ralph Waldo Emerson tries to do, we must take up some little thread or threads. and string our thoughts thereupon, keeping up also a relation among them of precession and succession."

2. The wobbling motion of the axis of a spinning body when there is an external force acting on the axis.
3. The slow gyration of the earth's axis around the pole of the ecliptic, caused mainly by the gravitational torque of the sun and moon.
4. Any of several slow changes in an astronomical body's rotational or orbital parameters.