Sex with eight-legs. Yes that means four people with two legs or eight people with one leg each.
Hey guys lets have some wicked Spider Sex!!"
Sex that is so good that it causes you to get "caught up" with feelings, emotions, or attachment towards the other individual when originally, you had no intentions of there being any strings attached.
"Man, she was just another chick from the club. Then she put that spider sex on me, and now she's my girl!"