Adjective: unpassable ,ún'pã-su-b(u)l
- Incapable of being passed
"For on the one side there is the sea, and on the other vast mountains and forests, unpassable to horsemen";
- impassable
- (of a law or motion) impossible to be passed or approved
"The controversial bill proved unpassable in parliament"
See also: unclimbable, unnavigable, unsurmountable, untraversable