Cucurbituril is a macrocyclic cavitand compound with two portals.是什么意思？

Cucurbituril is a macrocyclic cavitand compound with two portals.

葫芦脲是一种具有大环空腔、两端开口的葫芦状分子.

is

vt.& vi. 是（be的三单形式；n. 存在；

例句
Bollinger 'RD' is a rare, highly prized wine.
博林格RD香槟是一种名贵的备受推崇的葡萄酒。

macrocyclic

adj. 大环的；

例句
Cucurbituril is a macrocyclic cavitand compound with two portals.
葫芦脲是一种具有大环空腔、两端开口的葫芦状分子.

compound

n. 场地，复合物，（筑有围墙的）院子，复合词；

例句
This sticky compound adheres well on this surface.
这种黏性的化合物能牢牢地粘在这个表面上。

with

prep. 和，跟，随着，关于，和…一致；

例句
A waiter entered with a tray...
侍者端着托盘进来了。

two

n. 两个，两个东西，两点钟，一对；adj. 两个的，我

例句
He has been absent from his desk for two weeks...
他已经有两个星期没有坐在办公桌前了。

portals

n. 入口( portal的名词复数 )，桥门，[解剖学]肝门，出孔；

例句
The hallowed portals of academe were slowly and grudgingly opening to women.
大学神圣的大门缓慢又勉强地向女性敞开。