"Chumming together" refers to the act of spending time or socializing with close friends or companions. Antonyms for this phrase would include "soloing," which means spending time or doing something by oneself, or "isolating," which means separating oneself from others. Other antonyms for "chumming together" include "estranging," which means becoming distant or alienating oneself from others, and "staving off," which means avoiding social interaction altogether. In contrast to "chumming together," these antonyms suggest a lack of socialization or a desire to be alone.