1. an online forum member who is invisible as being active or online
2. an online forum member who posts very infrequently
1. userA: It doesn't show userB is online, but he just responded to my post.
userC: userB is a forum ghost. He may be here. He may not be.
2. userA: Where's userB and userD? They haven't responded for a week.
userC: They are forum ghosts. It may be a while before you get a response.