oversized breast cup
When the breast cup of a bra or leotard is noticeably too big for the breasts, and hangs loosely off the chest.
Usually seen with bras or Playboy bunnysuits. Bikinis and other skintight garments (spandex and the like) usually don't qualify since they are too tight. Also, the clothing in question must be more or less properly worn, to emphasize the size difference.
Examples
