Antonyms of adj impassable

1 sense of impassable

Sense 1
impassable (vs. passable), unpassable -- (incapable of being passed)

passable (vs. impassable) -- (able to be passed or traversed or crossed; "the road is passable")
        => navigable -- (able to be sailed on or through safely; "navigable waters"; "a navigable channel")
        => negotiable -- (capable of being passed or negotiated; "a negotiable road")
        => surmountable, climbable -- (capable of being surmounted)
        => traversable, travelable -- (capable of being traversed; "highway crews soon had the roads travelable")

Similarity of adj impassable

1 sense of impassable

Sense 1
impassable (vs. passable), unpassable -- (incapable of being passed)
       => unsurmountable, unclimbable -- (incapable of being surmounted or climbed)
       => unnavigable -- (incapable of being navigated)
       => untraversable -- (incapable of being traversed)