head nodding1
/ˈhɛd ˌnɒdɪŋ/noun
1The action or an act of nodding one's head to express assent, greeting, etc.
2The action of repeatedly, and often violently, nodding or shaking the head, as a form of headbanging; an instance of this.
Origin
Mid 19th century; earliest use found in London Journal. From head + nodding.
head-nodding2
/ˈhɛdˌnɒdɪŋ/adjective
1Engaged in nodding the head, especially to express assent or with drowsiness; characterized by such nodding of the head.
2Designating an appealing or gentle musical rhythm to which one might nod one's head; designating a piece of music having such a rhythm.
Origin
Mid 19th century. From head + nodding.