im·permeable \(ˈ)im, əm+\adjective Etymology: Late Latin impermeabilis, from Latin in- in- (I) + Late Latin permeabilis permeable — more at permeable : not permeable : not permitting passage (as of a fluid) through its substance : impassable, impervious < an impermeable stone > < a coat impermeable to rain > < an impermeable layer of scum > • im·permeableness\“+\noun • im·permeably\“+\adverb