A small nod of the head, done repetitively in synchronization with music. Denotes approval of music by the listener. Performed at concerts by concert-goers, or while listening to music by the listener.

Substituted for dancing by hipsters, who are too cool to dance.

Got the covid-19 vaccine

The bobbing of the head that crowds do at a show when they don't know what else to do with themselves; approval of the show, or complete confusion and puzzlement of how their bodies should move, react, and connect.