I can only think of one thing Nite-Line could mean and that's of an "adult nature". I may be wrong, but as far as I'm aware Glen Ballard wrote Nite-Line, so only he would really know what it's about. I think Nite-Line is a fairly weak song. I presume it was recorded for Thriller and how the song may be interprited may be a reason it has never been released. It's quite a strange subject.