Someone who goes into your friends list, selects someone from your top friends, and then proceeds to "warn" them about you. For example, if you are seen in this person's profile pic, the myspace terrorist will then message that person with "I see you are dating _____. Be careful." or "Stay the fuck away from my man!" Presumably, the goal is to cause a rift between the victim and whoever the terrorist assumes they are dating or are close friends with.
"Man, this fucking myspace terrorist hit up my girl today with some bullshit. She almost broke up with me."