noun

• (uncountable) Precedence.
• (physics, countable) The wobbling motion of the axis of a spinning body when there is an external force acting on the axis.
• (astronomy, uncountable) 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.
• Any of several slow changes in an astronomical body's rotational or orbital parameters.