Someone who is so anti-social that if you hang around them a lot, you will find yourself becoming like them. Sort of like you caught their leprosy.
I used to be the biggest thing ever at this school. Then, I started hanging out with this social leper and now I have to beg for people to hang out with me
someone who can ruin your status with others just by hanging out with you
Did you hear about poor Steve?
My point exactly. He is the football quaterback. Poor Steve met a social leper and now no one hangs with him anymore