1. A sign of assent or salutation or command
2. The act of nodding the head; SYN. nutation.

ETYM Old Eng. nodden; cf. Old High Germ. knoten, genuoten, to shake, and Eng. nudge.
1. To lower and raise the head, so as to indicate assent.
2. To let the head fall forward through drowsiness.
3. To express or signify by nodding.
4. To sway gently back and forth, as of flowers or tress in the wind; SYN. sway.
5. To be almost asleep.