A golden ball, split in two halves in a shower of multicolored confetti and streamers.
Like 🎉 Party Popper, commonly used to convey congratulations and celebration, as on New Year’s Eve, birthdays, wedding days, graduations, and other special occasions or good times more generally.
Its design across platforms—and inclusion in early sets from au by KDDI—suggest the emoji is a Japanese kusudama, a decorative ball used at such festive occasions as opening ceremonies.