ロック音楽を強いエネルギーで演奏する、またはロック音楽に合わせて思いきり踊ること。
"He put on his favourite album and rocked out alone in his bedroom for an hour."
Party on, Wayne. Party on, Garth.
— Wayne's World (1992 film) — the film's central theme of rocking out is encapsulated in this catchphrase, though the exact 'rock out' phrasing appears throughout the film.