Nutation

[noo-tey-shuh n, nyoo-] /nuˈteɪ ʃən, nyu-/

noun
1.
an act or instance of nodding one’s head, especially involuntarily or spasmodically.
2.
Botany. spontaneous movements of plant parts during growth.
3.
Astronomy. the periodic oscillation observed in the precession of the earth’s axis and the precession of the equinoxes.
4.
Mechanics. the variation of the inclination of the axis of a gyroscope to the vertical.
/njuːˈteɪʃən/
noun
1.
(astronomy) a periodic variation in the precession of the earth’s axis causing the earth’s poles to oscillate about their mean position
2.
(physics) a periodic variation in the uniform precession of the axis of any spinning body, such as a gyroscope, about the horizontal
3.
Also called circumnutation. the spiral growth of a shoot, tendril, or similar plant organ, caused by variation in the growth rate in different parts
4.
the act or an instance of nodding the head
n.

1610s, “action of nodding,” from Latin nutationem (nominative nutatio), noun of action from past participle stem of nutare “to nod,” from PIE *neu- “to nod” (see numinous). Astronomical use is from 1715. Related: Nutational.

nutation nu·ta·tion (nōō-tā’shən, nyōō-)
n.
The act of nodding the head, especially involuntarily.
nutation
(n-tā’shən)