"Be employed by" means to work for or to be hired by someone. Its antonyms would be "quit" or "resign," which both mean to give up or leave a job voluntarily. Another antonym is "get fired," which means to be dismissed from a job due to poor performance or misconduct. Additionally, "retire" is an antonym for "be employed by," which means to leave a job permanently after reaching a certain age. Lastly, "be self-employed" could also be considered an antonym for "be employed by," meaning to work for oneself instead of being hired by someone else.