1.VerbTo move one's head from side to side, in a repeated swiveling motion from the neck, to indicate disagreement, negation, disbelief, disapproval or dismay.
"She was shaking her head no."
2.VerbTo move one's head up and down, in a repeated hinge-like motion from the top of the spine, to indicate agreement, affirmation, approval, or simply polite attentiveness.