Nutation
Nutation , noun
[Latin nutatio a nodding, from nutare to nod: compare French nutation.]
1.
The act of nodding.
So from the midmost the nutation spreads,
Round and more round, o'er all the sea of heads.
2.
(Astronomy) 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.
(a) (Botany) 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)
(Botany) Circumnutation.