improbable
UK: ɪmˈprɒbəbl̩ | US: ɪmˈprɑːbəbl̩
adj. unlikely to be true or to happen
adj. difficult to believe; not probable
The word "improbable" originates from Latin improbabilis, combining the negative prefix im- (from in-, meaning "not") with probabilis ("provable" or "credible"). The root prob- derives from probare ("to test or prove"), reflecting the idea of something being "not capable of passing a test of truth." Over time, it evolved in Middle English via Old French to emphasize unlikelihood or doubtfulness. The morpheme -able reinforces the capacity for the root action, creating a cohesive meaning of "not able to be proven true."
The detective dismissed the suspect's improbable alibi.
It seems improbable that she could finish the project in one day.
His explanation sounded improbable, yet no one could disprove it.
Winning the lottery twice is statistically improbable.
The scientist considered the theory improbable but worth testing.