The phrase 'comes aboard' refers to someone joining a particular group or team. To find antonyms for this phrase, one can consider words that represent the opposite action, such as 'leaves', 'declines', 'resigns', 'withdraws', 'rejects', and 'quits'. These words imply a sense of separation or departure rather than joining or joining. For example, when an employee quits a job, they are leaving the team rather than joining it. Similarly, when someone declines an offer to join a group, they are indicating their intention to not become a part of it. In essence, antonyms for 'comes aboard' are words that denote the action of separating or distancing oneself from a particular group or team.