UNESCO tries to give an overall definition of the artist, which is, essentially, by self-identification:

"Any person who creates or gives creative expression to, or recreates works of art, who considers his artistic creation to be an essential part of his life, who contributes in this way to the development of art and culture and who is or asks to be recognised as an artist, whether or not he is bound by any relations of employment or association." (UNESCO 1980:5)

Frey & Pommerehne, researchers of cultural economics, enumerate eight commonly used methods for identifying artists (1989) ...