Nutation /(?)/

Nu·ta·tion

Nutation

n.
  1. The act of nodding.
    So from the midmost the nutation spreads, Round and more round, o'er all the sea of heads.
  2. 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. (Astron.)
  3. 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. (Bot.)