The idea is you gather in a tight circle, throw snowballs straight up and bend forward. Almost everybody gets hit, but since nobody knows by whom, there is no anger or retaliation.

大家围成一个紧密的圆圈，先向上投掷雪球然后弯下身子，差不多每个人都被雪球击中了，但是没有人知道自己是被谁投出的雪球击中的，所以既没有恼怒也无法报复。

youdao

The idea is you gather in a tight circle, throw snowballs straight up and bend forward. Almost everybody gets hit, but since nobody knows by whom, there is no anger or retaliation.

大家围成一个紧密的圆圈，先向上投掷雪球然后弯下身子，差不多每个人都被雪球击中了，但是没有人知道自己是被谁投出的雪球击中的，所以既没有恼怒也无法报复。

youdao