They overstayed their visa.是什么意思？

They overstayed their visa.

他们居留超过了签证期限。

they

pron. 他/她/它们，人们，大家，政府，当局，她们；

例句
The storms had abated by the time they rounded Cape Horn.
他们绕过合恩角时，暴风雨已经减弱。

their

pron. 他（她，它）们的，在提及性别不详的人时，用以代替 him 或 her；

例句
Their permissiveness toward their children reflects the wild abandon of their own lives.
他们对孩子的放任折射出他们自身生活的放浪形骸。

visa

n. 签证；vt. 签发签证；

例句
He had lived illegally in the United States for five years after his visitor's visa expired.
在访问签证到期后，他又在美国非法居住了5年。