Antonyms for "meet up with" could be phrases like "avoid meeting," "separate from," or "part ways from." When someone meets up with another person, they are coming together for a specific purpose, whether that be a social gathering, a work meeting, or just hanging out. Conversely, when avoiding meeting, people may consciously or unconsciously choose to not engage with others - this could mean keeping to themselves, staying away from social activities, or simply not approaching others. In some cases, people may separate from others due to disagreements or personal issues. "Parting ways from" could be used to describe people who end their relationship or choose to go their separate ways.