If a road, path, or route is impassable, it is impossible to travel over because it is blocked or in bad condition.
英汉词典释义
adj.
不能通行的,无法通过
The mud made the roads impassable.道路因为泥泞而无法通行。There was an impassable barrier between the white race and the one which they had reduced to slavery.在白色人种和被他们奴役的种族之间有一道不可逾越的障碍。