PERMEABLE

[adjective] [formal]If a substance is permeable, it allows liquids or gases to go through it.Certain types of sandstone are permeable to water.The solvent passes through the permeable membrane to the solution.Soft and gas-permeable contact lenses are kinder to the eyes than hard lenses.(figurative) Additional guards have been placed along the border and now it is less permeable than it once was (= fewer people are able to travel across the border illegally).