A painting
Seriously, I know we all knew the definition of “painting” – basically, painting is “next step” of drawing or sketching, we use color or paint instead pen or pencil. So it’s really hard to get a really good definition of painting according to reality because “painting” is painting.
But I still looking for it on the internet, by wikipedia:
Painting is the practice of applying paint, pigment, color or other medium to a surface (support base). The medium is commonly applied to the base with a brush but other implements, such as knives, sponges, and airbrushes, can be used. In art, the term painting describes both the act and the result of the action. However, painting is also used outside of art as a common trade among craftsmen and builders. Paintings may have for their support such surfaces as walls, paper, canvas, wood, glass, lacquer, clay, leaf, copper or concrete, and may incorporate multiple other materials including sand, clay, paper, gold leaf as well as objects.
Art Book 