When someone "muscles in" on something, they are forcing their way into a situation or conversation. Antonyms for this phrase would include phrases such as "yielded," "relinquished," or "backed off." These words indicate a sense of stepping back or giving up in a situation. Another antonym for "muscling in" could be "invited," suggesting that the person was asked to join the conversation or situation. Additionally, "respected" could be considered an antonym, implying that the person was acknowledged and accepted without pushing their way in. Overall, the antonyms for "muscling in" tend to convey a sense of willingness and cooperation, rather than forceful behavior.