Definition of "insuperable"

Regular services for passengers and goods were maintained for almost 50 years, but the speed limit of 16 m.p.h., imposed by the Board of Trade, proved an insuperable handicap after the introduction of competitive motor bus services.

1950 September, “The Southwold Railway”, in Railway Magazine, page 578

While Indian English may not have a uniform standard form throughout the country, this in itself is not an insuperable obstacle for lexicography.

2012, James Lambert, “Beyond Hobson-Jobson: A new lexicography for Indian English”, in World Englishes‎, page 308

For the first time I steadily reviewed the obstacles—and to consider them was at once to see they were insuperable.

1834, L[etitia] E[lizabeth] L[andon], Francesca Carrara. […], volume II, London: Richard Bentley, […], (successor to Henry Colburn), pages 4–5