the world > movement > motion in specific manner > alternating or reciprocating motion > move to and fro or up and down [verb (intransitive)] > nod the head (6)
intransitive. To make a brief inclination of the head, esp. in salutation, assent, or command, or to draw attention to something.
intransitive. To nod or shake the head. Obsolete.
transitive. To nudge or prod. Also: to nod (the head).