The term BYGONE SERF is a combination of two words, 'BYGONE' and 'SERF'. BYGONE means something that is no longer in existence or has passed away, while SERF is an agricultural laborer in the feudal system of the Middle Ages who was bound to the land and owned by a lord. The crossword solution for this term is HELOT, which is a Greek term for a person in a state of servitude, similar to a SERF. Therefore, the term BYGONE SERF can be defined as a person who was once bound to the land and owned by a lord, but is no longer in existence.