At the moment:

I think a work of art is any discrete, non-inevitable phenomena emerging through the active and idiomatic influence of a small number of humans, which has subsequently accreted a critical mass of relevance to other humans.

What a mouthful! I'll unpack this later. I'm doing a bit of exploratory writing as research for an upcoming series of sculptures, and apparently I needed to define what I felt could encompass what I think of as "art". Now I'll go work on my concept of "coffee" and "lunch."