General synonyms:
* Semipermeable: This is a very common synonym, often used interchangeably with "selectively permeable".
* Differential permeability: This emphasizes the difference in how different substances are allowed to pass through.
* Permeable with selectivity: This is a more descriptive phrase that clarifies the selective nature of the permeability.
More specific alternatives:
* Permselective: This term is used more often in technical contexts related to membrane technology.
* Selective: This emphasizes the choice aspect of the permeability, but it's less specific to the context of membranes.
* Partially permeable: This can be used if the focus is on the limited permeability, rather than the selectivity.
The best word or phrase to use depends on the specific context and the intended meaning.