Said when an event or performance has come to an end, or when someone or something has left a place, especially in a dramatic fashion. The phrase refers to an announcement famously made at the end of Elvis Presley concerts alerting people that he vacated the premises and no further encores would be played. We kept waiting for the band to come back on stage to perform some of the fans' favorite songs, but it looked like Elvis had left the building. That ball is flying, and it looks like... yes, it's a homerun! Elvis has left the building, folks!