N closure, occlusion, blockade, shutting up, obstruction, embolus, contraction, infarction, constipation, obstipation, blind alley, blind corner, keddah, cul-de-sac, caecum, imperforation, imperviousness, impermeability, stopper, closed, shut, operculated, unopened, unpierced, imporous, caecal, closable, imperforate, impervious, impermeable, impenetrable, impassable, unpassable, invious, pathless, wayless, untrodden, untrod, unventilated, air tight, water tight, hermetically sealed, tight, snug.

For further exploring for "unopened" in Webster Dictionary Online