open door
noun
in sing.
1- a free or unrestricted means of admission or access免费开放; 自由进出：
being homeless is not an open door to decent housing.
无家可归并不意味着能住上像样的住处。
1.1
- the policy or practice by which a country allows the free admission of immigrants or foreign imports门户开放（政策）：
as modifier an open-door immigration policy.门户开放的移民政策。