离港证的英文：
clearance label

clearance是什么意思：
n. 清除，清扫；清仓甩卖；空隙；放行证

take off clearance = clearance for take off
起飞许可

The plane was given clearance to land.
飞机被给予着陆的许可。

Clearance of this check could take a week.
支票兑现可能需要一个星期。

The clearance work will enable the garden to look as attractive as possible.
清扫工作将使这座花园尽可能地景色宜人。

Why not cure unemployment by a National Slum clearance effort?
何不通过全国性的消除贫民窟运动来解决失业问题呢?

label是什么意思：
n. 标签；绰号；唱片公司
v. 贴标签于；（尤指不公正地）把...称为

Put a label on your luggage.
在你行李上做个标记。

The bottle is labeled poison.
瓶子上表明有毒。

Certain estates are labelled as undesirable.
某些物业被归入不受欢迎之列。

Please unveil the label firstly.
请先揭开标签。

This phrase is labelled as an Americanism in the dictionary.
这本词典把这个短语称为美国特有的语言现象。