The word "inconceivable" is often used to describe something that is impossible to imagine or beyond belief. Its antonym, conceivable, means that something is possible, imaginable, or believable. Other antonyms for inconceivable include plausible, thinkable, logical, and reasonable. These words imply that there is a chance of something happening or being true. On the other hand, antonyms such as impossible, unbelievable, and unimaginable all suggest that there is no chance of something happening. Therefore, while inconceivable and its antonyms all deal with the realm of possibilities, they differ in whether or not they imply a likelihood of occurrence.