Assertable means able to be stated or affirmed confidently. Therefore, the antonyms for assertable would be terms that signify doubt, uncertainty or disavowal. Some possible antonyms could include words like uncertain, doubtful, questionable, refutable, contestable, and speculative. Other antonyms might be contradictory, negated, denied, or disproven. Using these antonyms to describe a statement or theory could indicate that it lacks clear evidence or proof, or that it conflicts with established facts or beliefs. Being aware of antonyms for assertable can help to clarify the level of certainty or confidence that is being conveyed in communication.