The phrase "hadst business with" is a dated and formal way of saying "had dealings with" or "had a conversation with." Antonyms for this phrase might include "uninvolved," "ignorant," or "unconcerned." These words suggest a lack of engagement or interest in a particular subject or situation. Other antonyms might include "disinterested," "disengaged," or "distant," which all imply a sense of detachment or detachment from a situation or relationship. In contrast, synonyms for "hadst business with" might include "engaged with," "involved in," or "connected to," all of which suggest a sense of active participation or engagement with a particular person, group, or activity.