"Realism is commonly defined as a concern for fact or reality and rejection of the impractical and visionary. However, the term realism is used, with varying meanings, in several of the liberal arts; particularly painting, literature, and philosophy. It is also used in international relations."
In the visual arts and literature, realism is a mid-19th century movement, which started in France. The realists sought to render everyday characters, situations, dilemmas, and events; all in an "accurate" (or realistic) manner. Realism began as a reaction to romanticism, in which subjects were treated idealistically. Realists tended to discard theatrical drama and classical forms of art to depict commonplace or 'realistic' themes.
American Realism is an artistic movement in the USA that was active in literature, photography, and painting from 1880 to 1940. One of it's main representatives is Edward Hopp
In business though, I found two good definitions:
1.Practical or pragmatic (as opposed to idealistic or visionary) orientation that relies on 'hard facts,' and considers things as they are and not on what they might or should be. In politics, realism is called realpolitik.
"I would never write realistic prose. I don't like people who try to write in a poetic style, but in the course of their book abandon it for realism, and weave back and forth like drunkards between the surreal and the real."