The phrase "having a hunch" typically refers to having an instinctive feeling or intuition about something without concrete evidence. Antonyms for this phrase could include words like "certain," "definite," "conclusive," or "evident." These words all suggest a high degree of confidence and concrete evidence to support a belief or decision, as opposed to a vague or uncertain sense of intuition. Other antonyms for "having a hunch" might include "ignorant," "clueless," or "uninformed," which all suggest a lack of knowledge or insight into a given situation. Ultimately, the opposite of "having a hunch" is having a well-informed, clearly supported belief or decision.