The word "foolable" refers to a person or a situation that can easily be deceived or fooled. Antonyms for "foolable" would, therefore, imply a difficult or impossible task to deceive or be fooled. Some antonyms for "foolable" include wise, shrewd, astute, perceptive, discerning, sharp, and insightful. Other possible antonyms include skeptic, unimpressed, and incredulous. These words signify a level of discernment or skepticism that implies immunity to deceit. In contrast to "foolable," these antonyms connote a high level of intelligence and the ability to see through any dishonest or misleading behavior.