1. 正门；宏伟的大门
A portal is a large impressive doorway at the entrance to a building.

2. 门户（网站）
On the Internet, a portal is a site that consists of links to other websites.

1. a grand and imposing entrance (often extended metaphorically)

e.g. the portals of the cathedral
the portals of heaven
the portals of success

2. a short vein that carries blood into the liver

Synonym: portal veinhepatic portal veinvena portae

3. a site that the owner positions as an entrance to other sites on the internet

e.g. a portal typically has search engines and free email and chat rooms etc.

Synonym: portal site