2. The study of form, or the branch of science that studies the physical structure of animals, plants, and other organisms.
3. The physical structure; especially, the internal structure, of an animal, plant, or other organism, or of any of its parts.
Gross anatomy involves structures that can be seen with the naked eye. It is the opposite of "microscopic anatomy" (or histology) which involves structures seen under the microscope.
Traditionally, both gross and microscopic anatomy have been studied in the first year of medical school in the U.S. The most celebrated textbook of anatomy in the English-speaking world is Gray's Anatomy, still a useful reference book.
The word anatomy comes from the Greek ana-, "up" or "through" + tome, "a cutting". Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it; that is, cutting it up.