impermeable

1 impossible to get through or into the wall of security people surrounding the rock band was impermeable Synonyms impassable (also impassible), impenetrable, impervious, impregnableRelated Words close, compact, dense, thick, tight; compressed, condensed; sturdy, substantial, tough; firm, frozen, hard, solid, stiff; inflexible, rigid, unbending, unyieldingNear Antonyms soft, squishy; bendable, elastic, flexible, giving, malleable, pliable, yielding; absorbent, porousAntonyms negotiable, passable, penetrable, permeable

2 not allowing penetration (as by gas, liquid, or light) an impermeable seal on the ancient tomb had preserved the artifacts exceptionally well Synonyms impenetrable, tight, imperviousRelated Words close, compact, dense, snug, thick; airtight, hermetic (also hermetical), leakproof, watertight; lightproof, soundproof, waterproofNear Antonyms absorbent, leaky, porous, unsealedAntonyms penetrable, permeable, pervious