specifically when listening to music, to lose oneself to the music, to get into a zone or zone-out while listening to a particularly engrossing piece of music, beat, or set of rap lyrics. Most applicable when used in reference to listening to music.

when you're hungover as shit after a spending a night drunk as a skunk

to chill out, relax, max.

just relaxing, chilling, listening to some mellow music
may or may not be stoned