nod

intransitive verb nodded, nodding

1. to bend the head forward slightly and raise it again quickly, as a sign of greeting, command, acknowledgment, invitation, or, specif., of agreement or assent
2. to let the head fall forward involuntarily because of drowsiness; be very sleepy
3. to be inattentive or careless; make a slip
4. to sway back and forth or up and down, or to hang down, as the tops of trees, flowers, plumes, etc.
5. Slang to be under the influence of a drug, as heroin

transitive verb

1. to bend (the head) forward slightly and raise it again quickly
2. to signify (assent, approval, agreement, etc.) by doing this
3. to invite or dismiss by a nod

noun

1. a nodding, as of the head, treetops, etc.
2. a sign of affirmation, assent, favorable decision, etc.: to give or get the nod