The phrase "fixt up on" refers to being infatuated or enamored with someone or something. The antonyms for "fixt up on" would be "disenchanted," "repelled," or "uninterested." Disenchanted implies a loss of interest or disillusionment, while repelled suggests a deep aversion towards someone or something. Uninterested, on the other hand, simply means lacking enthusiasm or curiosity. These antonyms are useful in describing the opposite sentiment to being fixt up on something or someone, and can provide a nuanced understanding of how people can react differently to the same thing.