why not just look at other definitions an easy way would with
sculpture :Three-dimensional art produced especially by forming hard or plastic materials into three-dimensional objects, usually by carving or modeling. The designs may be produced in freestanding objects (i.e., in the round), in relief, or in environments, and a variety of media may be used, including clay, wax, stone, metal, fabric, wood, plaster, rubber, and found objects. Materials may be carved, modeled, molded, cast, wrought, welded, sewn, or assembled and combined.
So we can go the easy way and say
Bonsai : Three dimensional art produced by forming or modifing contained trees or scrubs into three dimensional objects, usually by carving or modeling. The desings may be produced in freestanding objects (i.e., in the round), in relief, or in contained environments, and a variety of species may be used.
This is a simple definition, for both but well, and yes who is to say what art is, definetly not the british!!! just jocking after reading bonsai is not an art written by Walter. funny stuff, but probably the british art council was not educated about bonsai and just see the definition of tree in pot or plant in pot, and therefore you get no funding (at least from the british art council)
Obviously in the simple definition there will be words we can?t define,
Art, Soul, life! etc they have different meanings, and some like life our ignorance does not allow a good definition for it. So basically there are several degrees of freedom from each person, which depend on their knoledge to see and taste differently. The artistic trees I loved as a child I wold not consider artistic any more!