The term "selectee" refers to someone who has been selected or chosen for a particular position or opportunity. A few antonyms that could be used for the term "selectee" include "reject," "unselected," "unchosen," or "not selected." These words convey a sense of disappointment, as they suggest that the person in question was not chosen for the role or opportunity they were hoping for. Other antonyms could include "loser," "outsider," or "outcast," which have a more negative connotation and imply a sense of exclusion or rejection from a group or community. Ultimately, the choice of antonym will depend on the context in which it is being used and the overall tone of the text.