from thoughtco.com: The Tate Gallery's glossary says the term painterly "carries the implication that the artist is reveling in the manipulation of the oil paint itself and making the fullest use of its sensuous properties."
a good example can be found in any detail of a van gogh painting. the thoughtsco article goes on to say: a style that celebrates the medium that it was created in, ….rather than a style that tries to hide the act of creation or the medium used. It is a loose and expressive approach to the process of painting in which the brushstrokes (or even knife strokes, if any paint was applied with a palette knife) are visible.
if you make this van gogh detail larger by clicking on it, you will see a perfect example of the painterly.
this quality is central to my work, and has been for my entire career. for the casual viewer, who may not have a grasp of the history of art, it’s a quality more easily understood and appreciated in a realist painting than in an abstract or, in my case, abstracted painting. in the small painting i made yesterday: frozen creek, it becomes easier to identify this quality after having had even a perfunctory introduction such as the one i’ve provided here.