My first answer was disingenuous, so here's another interpretation.

I didn't see a definition in the article, however I was reading Edgar Payne's Compostion of Outdoor Painting after reading your comment, and I was surprised to find the book talked about problem finding.

"Art is the art of disguising art". This means artists have to make a representation of a material object while obscuring all the rules and principles required to make the representation.

The problem is: how to make art without making it blatantly obvious it was an effort to make?