What is art?

In my art history class, our class is discussing this idea of "what is art?"

Is this art?

What about this?

Does art need to have visual appeal? 

Because I think this doll is rather scary but someone considers it art. 

What about forgeries? (Matt Bomer anyone...??)

I believe this is a never ending cycle of questions.  So - what is your answer to "What is art?"