What is the meaning of nod?

noun

• A sign of assent or salutation or command.
• The act of nodding the head.

verb

• Express or signify by nodding.
  • usage: "He nodded his approval"
• Lower and raise the head, as to indicate assent or agreement or confirmation.
  • usage: "The teacher nodded when the student gave the right answer"
• Let the head fall forward through drowsiness.
  • usage: "The old man was nodding in his chair"
• Sway gently back and forth, as in a nodding motion.
  • usage: "the flowers were nodding in the breeze"
• Be almost asleep.
  • usage: "The old man sat nodding by the fireplace"