Nod - Definition
nod
n 1: a sign of assent or salutation or command
2: the act of nodding the head
v 1: express or signify by nodding; "He nodded his approval"
2: lower and raise the head, as to indicate assent or agreement
or confirmation; "The teacher nodded when the student gave
the right answer"
3: let the head fall forward through drowsiness; "The old man
was nodding in his chair"
4: sway gently back and forth, as in a nodding motion; "the
flowers were nodding in the breeze"
5: be almost asleep; "The old man sat nodding by the fireplace"