unacquaintance 

Unfriend someone on Face Book who isnt a friend just a mere acquaintance. Someone you' ve seen in a throw back picture from Infant School.

Im gonna unacquaintanceyou. You werent ever my friend

unacquaintance by linzy173 March 11, 2014

unicquaintance 

A person known to the speaker, but who does not know the speaker.
A manufactured word using the prefix "uni" and "acquaintance" to describe a phenomenon previously unlabeled by a single word.

I've heard plenty about Carol in accounting, but I'm sure she has no idea who I am. I consider her a unicquaintance.

unicquaintance by Ben Timberlake December 30, 2005