NUTATION
nutation
(noun) uncontrolled nodding
Source: WordNet® 3.1
Etymology
Noun
nutation (countable and uncountable, plural nutations)
(physics) A bobbing motion that accompanies the precession of a spinning rigid body.
A nodding motion (of the head etc.).
(astronomy) Any of several irregularities in the precession of the equinoxes caused by varying torque applied to the Earth by the Sun and the Moon.
(botany) The circular motion of the tip of a growing shoot.
Source: Wiktionary
Nu*ta"tion, n. Etym: [L. nutatio a nodding, fr. nutare to nod: cf. F.
nutation.]
1. The act of nodding.
So from the midmost the nutation spreads, Round and more round, o'er
all the sea of heads. Pope.
2. (Astron.)
Definition: 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.
3. (Bot.)
(a) The motion of a flower in following the apparent movement of the
sun, from the east in the morning to the west in the evening.
(b) Circumnutation.
Source: Webster’s Unabridged Dictionary 1913 Edition