Word Study
impassable
CIDE DICTIONARY
impassable, a. [Cf. Unpassable.].
Incapable of being passed; not admitting a passage; as, an impassable road, mountain, or gulf. [1913 Webster]
OXFORD DICTIONARY
impassable, adj. that cannot be traversed.
Derivative
impassability n. impassableness n. impassably adv.
ROGET THESAURUS
impassable
Closure
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.Impossibility
N impossibility, what cannot, what can never be, sour grapes, hopelessness, impossible, not possible, absurd, contrary to reason, unlikely, unreasonable, incredible, beyond the bounds of reason, beyond the bounds of possibility, beyond the realm of possibility, from which reason recoils, visionary, inconceivable, prodigious, unimaginable, inimaginable, unthinkable, impracticable unachievable, unfeasible, infeasible, insuperable, unsurmountable, insurmountable, unattainable, unobtainable, out of reach, out of the question, not to be had, not to be thought of, beyond control, desperate, incompatible, inaccessible, uncomeatable, impassable, impervious, innavigable, inextricable, self- contradictory, out of one's power, beyond one's power, beyond one's depth, beyond one's reach, beyond one's grasp, too much for, ultra crepidam, the grapes are sour, non possumus, non nostrum tantas componere lites, look for a needle in a haystack, chercher une aiguille dans une botte de foin, il a le mer +a boire.For further exploring for "impassable" in Webster Dictionary Online