Counterassert is a verb that means to assert the opposite of what has been said or claimed. It is a strong way to contradict or negate a statement. Some synonyms for counterassert include refute, deny, contradict, oppose, challenge, rebut, and disprove. These words all convey a sense of going against what someone else has said or claimed, often in a forceful or convincing way. Using synonyms for counterassert can help to add more variety and complexity to language. When employed properly, they can help to convey a greater sense of nuance and intellectual rigor to discussions and debates.