(1):
(n.) Specif., the principles and characteristics professed or represented by a 19th-century school of realistic writers, notably by Zola and Maupassant, who aimed to give a literal transcription of reality, and laid special stress on the analytic study of character, and on the scientific and experimental nature of their observation of life.
(2):
(n.) The theory that art or literature should conform to nature; realism; also, the quality, rendering, or expression of art or literature executed according to this theory.
(3):
(n.) The doctrine of those who deny a supernatural agency in the miracles and revelations recorded in the Bible, and in spiritual influences; also, any system of philosophy which refers the phenomena of nature to a blind force or forces acting necessarily or according to fixed laws, excluding origination or direction by one intelligent will.
(4):
(n.) A state of nature; conformity to nature.