the directional change of the axis of a rotating body

Precession is the directional change of the axis of a rotating body (a gyroscope) when external forces apply torque to torque .

The change in direction of the angular momentum vector due to an applied torque

The change in direction of the angular momentum vector due to an applied torque is called precession.

a rotation of the Earth's rotation axis

Precession is a rotation of Earth's rotation axis, caused primarily by external torques from the gravity of the Sun, Moon and other bodies.

a slow gyration of the Earth’s rotational axis caused by the effects of the Sun and Moon

Precession is a slow gyration of the Earth’s rotational axis caused by the effects of the Sun and Moon and altering the position of the vernal equinox against the background sky.

a wobble in the Earth's axis of rotation (called precession)

However, a wobble in the Earth's axis of rotation (called precession), means that the positions of the stars changes gradually over time.