A very unpleasant or
stupid person. In
case you are not yet convinced that someone is a cunt
noun, the related adjective, "cuntable", can be applied.
"He has been a very successful businessman as a former hedge fund
manager and a CEO at many other companies, yes, but ,if you
get closer to him, then you can see he's such a heartless and merciess idiot. In other
words, he's a cunt noun."