NOUN (2)

1. a sign of assent or salutation or command;

2. the act of nodding the head;


VERB (5)

1. express or signify by nodding;
- Example: "He nodded his approval"

2. lower and raise the head, as to indicate assent or agreement or confirmation;
- Example: "The teacher nodded when the student gave the right answer"

3. let the head fall forward through drowsiness;
- Example: "The old man was nodding in his chair"

4. sway gently back and forth, as in a nodding motion;
- Example: "the flowers were nodding in the breeze"

5. be almost asleep;
- Example: "The old man sat nodding by the fireplace"

The Collaborative International Dictionary of English v.0.48:

Nod \Nod\, v. t. [imp. & p. p. Nodded; p. pr. & vb. n.
   Nodding.]
   1. To incline or bend, as the head or top; to make a motion
      of assent, of salutation, or of drowsiness with; as, to
      nod the head.
      [1913 Webster]

   2. To signify by a nod; as, to nod approbation.
      [1913 Webster]

   3. To cause to bend. [Poetic]
      [1913 Webster]

            By every wind that nods the mountain pine. --Keats.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nod \Nod\ (n[o^]d), v. i. [OE. nodden; cf. OHG. kn[=o]t[=o]n,
   genuot[=o]n, to shake, and E. nudge.]
   1. To bend or incline the upper part, with a quick motion;
      as, nodding plumes.
      [1913 Webster]

   2. To incline the head with a quick motion; to make a slight
      bow; to make a motion of assent, of salutation, or of
      drowsiness, with the head; as, to nod at one.
      [1913 Webster]

   3. To be careless or inattentive; to make a mistake from lack
      of attention.
      [1913 Webster]

            Nor is it Homer nods, but we that dream. --Pope.
      [1913 Webster]

   4. To be drowsy or dull; to doze off, especially while in a
      sitting position; as, half the class nodded while the
      professor droned on.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Nod \Nod\ (n[o^]d), n.
   1. A dropping or bending forward of the upper part or top of
      anything.
      [1913 Webster]

            Like a drunken sailor on a mast,
            Ready with every nod to tumble down.  --Shak.
      [1913 Webster]

   2. A quick or slight downward or forward motion of the head,
      in assent, in familiar salutation, in drowsiness, or in
      giving a signal, or a command; as, a nod of approval.
      [1913 Webster]

            A look or a nod only ought to correct them [the
            children] when they do amiss.         --Locke.
      [1913 Webster]

            Nations obey my word and wait my nod. --Prior.
      [1913 Webster]

   The land of Nod, sleep.
      [1913 Webster]

WordNet (r) 3.0 (2006):

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"