nutation

The act or an instance of nodding the head.

A wobble in a spinning gyroscope or other rotating body.

A small periodic irregularity in the precessional motion of the earth’s polar axis with respect to the pole of the ecliptic.

A slight curving or circular movement in a stem, as of a twining plant, caused by variation in growth rates of different parts.

A nodding.

In pathology, a constant nodding or involuntary shaking of the head.

In astronomy, a small subordinate gyratory movement of the earth’s axis, in virtue of which, if it subsisted alone, the pole would describe among the stars, in a period of about nineteen years, a minute ellipse, having its longer axis directed toward the pole of the ecliptic, and the shorter, of course, at right angles to it.

In botany, same as circumnutation.

The act of nodding.

A very small libratory motion of the earth’s axis, by which its inclination to the plane of the ecliptic is constantly varying by a small amount.