An artistic mode in which forms are based closely on direct observation of the visible world rather than on strong stylization or abstraction.
Naturalism describes an artistic approach in which the representation of a subject is based, or appears to be based, on direct observation of the visible world. In sculpture this can involve close attention to anatomy, weight, proportion, surface, gesture, age, and the behavior of living form.
Naturalism is not identical to realism. A sculpture may be naturalistic while still idealizing or selectively refining the subject. The term is therefore useful when describing the gradual movement from schematic or highly conventionalized figures toward more observed bodily structure.
Etymology
From Latin natura, “nature,” through later European forms of the word naturalism.
Sculptor Notes
For a sculptor, naturalism is not simply the accumulation of anatomical detail. It depends on convincing structure: weight through the skeleton, compression and tension in the body, believable transitions of plane, and forms that behave as living forms do.
References
https://www.getty.edu/vow/AATFullDisplay?subjectid=300311115