An unwritten (or written) list of individuals a person keeps that they find unfuckable.
Out of all the people I wouldn't do, Eric is at the top of my Unfuckable List. There ain't enough alcohol in the world for me fuck him.
The unwritten (or written) list a person keeps of the most Un-Fuckable people they know.
I just heard that Eric ****** is at the top of every woman in Eastern Idaho's UF List. What a hideous bastard he must be.