Antonyms of adj supposable

1 sense of supposable

Sense 1
presumable, supposable, surmisable -- (capable of being inferred on slight grounds)

INDIRECT (VIA thinkable) -> unthinkable -- (incapable of being conceived or considered)

Similarity of adj supposable

1 sense of supposable

Sense 1
presumable, supposable, surmisable -- (capable of being inferred on slight grounds)
       => thinkable (vs. unthinkable) -- (capable of being conceived or imagined or considered)