Nutation
Pronunciation : Nu*ta"tion
Part of Speech : n.
Etymology : [L. nutatio a nodding, fr. nutare to nod: cf. F. nutation.]
Definition : 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.)
Defn: 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