Antonyms for the phrase "chumming around" might include words such as avoiding, alienating, distancing, or isolating. These terms suggest a lack of camaraderie or a deliberate effort to keep oneself apart from others. Other antonyms could include disengaging, partitioning, separating or segregating. These terms denote clear lines of separation or division, which may suggest a more rigid or formal relationship between individuals. Additionally, antonyms could also include words related to conflict or competition, such as competing, fighting, or opposing, which can indicate a sense of tension or hostility between individuals.