improbable
adj.not likely to happen or be true. You use this when something is possible but very surprising or hard to believe.
adj.unlikely to occur or be true; lacking a high degree of probability. Often used to describe events or explanations that seem far-fetched despite being possible.
“It is highly improbable that it will snow in July.”
“The detective found the suspect's story highly improbable, as it relied on too many coincidences.”
“The team's victory was an improbable outcome given their significant injuries and the strength of the opposing side, yet they managed a narrow win in the final minutes.”
Often modified by degree adverbs like 'highly', 'extremely', or 'utterly'.
“But when, in a stroke of fortune so improbable that even now it hardly seems real, her daughter, Raine, became Diana Spencer’s stepmother, Cartland sensed new opportunities for cross-pollination.”
“Some particularly improbable accounts claimed that African American mothers rented out their babies to hunters seeking to attract the reptiles.”
Borrowed from Latin improbābilis. By surface analysis, im- + probable.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.