impassable

Adjective

impassable (comparative more impassable, superlative most impassable)

1. (usually, terrain) Incapable of being passed over, crossed, or negotiated.
   • At the same time, the encroachment of vegetation proceeds apace, and broom and brambles have already made portions of the line impassable, even on foot.1949 November and December, “Notes and News: Festiniog and Welsh Highland Railways”, in Railway Magazine, page 408
   • [...] at Cowley Bridge Junction, east of Exeter, both lines were impassable from about 1.30 p.m.—the first flooding of the junction for 36 years—and by the evening the water had risen two-thirds of the way up the platforms at St. Davids as Exeter faced its worst flooding for 60 years.1960 December, “Talking of Trains: The railway and the Devon floods”, in Trains Illustrated, page 709
2. Incapable of being overcome or surmounted.
3. Not usable as legal tender.