Most cogitable means easily imaginable or readily conceivable. Therefore, the antonyms for the word would be vague, unimaginable, unpredictable, ambiguous, incomprehensible, odd, mysterious, unthinkable, unconvincing, incredible, and bewildering. These words denote a lack of clarity or a difficulty in understanding the meaning or concept associated with most cogitable. For instance, a situation could be undecipherable or inexplicable, making it tough to imagine or conceive. Thus, most cogitable's antonyms depict the absence or lack of clarity, precision, or knowledge essential for easy imagination or conception.