the age of sixteen for a girl, derived from the character 瓜 guā being split into two 八 bā (eights)

正值破瓜之年的她，对未来充满了无限的憧憬。

the age of sixty-four for a man, derived from multiplying two 八 bā (eights) from the character 瓜 guā

他已届破瓜之年，决定辞官归隐，安度晚年。

to lose one's virginity or to deflower a girl

在旧式小说中，常用“破瓜”一词委婉地描述女子初次行房。