The term 'ON-LINE FILTER TARGET' refers to the process of filtering out unwanted emails, such as spam. The crossword solution for this term is SPAM, which stands for 'Spoofed or Spamming Protocols Against Malicious Email'. This acronym is used to describe the process of identifying and blocking malicious emails from entering a user's inbox. By using an online filter target, users can protect themselves from receiving unwanted emails and protect their personal information from being accessed by malicious actors.