Historically, this term refers to a tight-fitting sleeveless garment for the torso and bust, which was common in Europe during the 16th to the 18th century
New plus size spring styles available at Ashley Stewart
Colors: Ivory, Blue, Yellow, Green
Bottom line: wear a dress to the gym, or whatever makes you feel like you can be the GOAT.
As further context, BeautifulExplorer363 said that she never actually asked Mia to be in her bridal party and that her future mother-in-law announced that Mia was a bridesmaid at a family gathering
(The dancers think he is there for the Chinese New Year number that is coming up later.) In the Futurama episode "A Tale Of Two Santas", Amy wears a midriff-baring Santa suit and skirt during the aforementioned I Am Spartacus scene