I know how this is going to sound but... here goes.
yet another way of choosing to define "art", and there are two requirements.
1) the artist, using "whatever" medium whatsoever... is trying to convey some emotion, abstractly.
2) the person experiencing this thing they made, feels some emotion, and this work caused it.
if you meet those 2, its "art"
if the artist is trying to convey emotion X, and the person experiences the same emotion X, then the art was successful.
the better the artist, the more people can connect to the same (intended) emotion.
the better the artist, the more emotions they can convey and the more people pick them all up.
a really good singer, or guitar player? can make you feel sad, or wistful, or happy or even energetic or angry... that's an artist.
the poet? if it stirs emotions, thats art.
as writers, when we learn to carry some emotional impact (make the reader cry, for example) thats art.
when emotion gets transferred, from maker to person experiencing, with no explanation... thats art.