In the Friends theme tune, the line "your love life's DOA" is an abbreviation for "dead on arrival." It means that the person's love life is not going well or is essentially non-existent. The phrase "dead on arrival" is commonly used to describe something that is doomed from the start or has failed before it even began. In the context of the song, it's likely referring to the challenges and struggles the person is facing in their romantic relationships.