I took a short college course that asked that exact question.
My feeling, everything is an art form. And it goes beyond the visual, and is a full sensory experience.
I remember standing at the class looking at a lamppost. Is that art? Of course it is.
Is nature art? It is by far, the grandest art form in existence. The human body is one of the most beautiful art forms there is, so yes, you are a piece of art.
Is heavy metal music art? My son thinks its the best art there is...art for him (I grit my teeth during it, so I guess I am "experiencing" it).
Is smearing crap on a canvas art? Yep, totally.
What do you think? Do you think there is anything that would not qualify as "art"?