The moment in a song where the refrain comes around for one last time, tempo dramatically slows down, and volume increases to full. Tempo often increases a few bars after for a flashy finish.
Common in modern production numbers, where the entire ensemble gets to sing and tap their hearts out. It doesn't have to be the entire chorus, though... or from a musical.
Often used to lead into a Big Rock Ending
. Compare Truck Driver's Gear Change