Antonyms of adj demonstrable

2 senses of demonstrable

Sense 1
demonstrable, incontrovertible -- (necessarily or demonstrably true; "demonstrable truths")

INDIRECT (VIA incontestable) -> contestable -- (capable of being contested)

Sense 2
demonstrable, provable -- (capable of being demonstrated or proved; "obvious lies"; "a demonstrable lack of concern for the general welfare"; "practical truth provable to all men"- Walter Bagehot)

INDIRECT (VIA obvious) -> unobvious -- (not immediately apparent; "in mathematical science connections are exhibited which...are extremely unobvious"- A.N.Whitehead)

Similarity of adj demonstrable

2 senses of demonstrable

Sense 1
demonstrable, incontrovertible -- (necessarily or demonstrably true; "demonstrable truths")
       => incontestable (vs. contestable), incontestible -- (incapable of being contested or disputed)

Sense 2
demonstrable, provable -- (capable of being demonstrated or proved; "obvious lies"; "a demonstrable lack of concern for the general welfare"; "practical truth provable to all men"- Walter Bagehot)
       => obvious (vs. unobvious) -- (easily perceived by the senses or grasped by the mind; "obvious errors")