Taylor Swift gave a preview of what's to come with her upcoming album, telling a packed house in Melbourne she was "lonely" during the quarantine ... and it's a clear shot at Joe Alwyn.

Just before TS sang "Betty" -- a song written during the pandemic -- she painted herself as a "ghostly Victorian lady" ... joking it was a departure from a "lonely millennial woman covered in cat hair, drinking my weight in white wine."

Joe co-wrote some of the songs on the album -- "Folklore" -- and also helped produce it.

The fact that she described herself as lonely speaks volumes, and forecasts what she'll sing about in her soon-to-be-released album "The Tortured Poets Department." Fans expect her to scorch Joe, with whom she broke up in April, 2023.

Taylor's had a tough week ... a 16-year-old fan died a few days ago en route to her Eras concert in Melbourne. And, as you know, she's been a huge Kansas City Chiefs booster, and donated $100k to the family of the woman who was shot and killed after the Super Bowl parade shooting.