opening a decorative ball filled with confetti, streamers, etc. at a celebration
Refers to the act of breaking open a くす玉 (a hanging ornamental ball) to release confetti, streamers, or a banner, typically at parties, ceremonies, or store openings.
See also: くす玉
At the end of the party, everyone did the kusudama-wari (opening of the decorative ball).
A kusudama-wari was performed at the opening ceremony of the new store.
Compound of くす玉 (ornamental ball) and 割り (breaking, from 割る). The exact origin of the practice is uncertain, but it is a modern celebratory custom in Japan.