(1):
(n.) The act of nodding.
(2):
(n.) Circumnutation.
(3):
(n.) 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.
(4):
(n.) 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.