noun
: the articulated series of vertebrae connected by ligaments and separated by more or less elastic intervertebral fibrocartilages that in nearly all vertebrates forms the supporting axis of the body and a protection for the spinal cord extending from the hind end of the skull through the median dorsal part of the body and to the end of the tail : backbone , spine ; broadly : the axial skeleton of the trunk and tail of a vertebrate which in the lowest vertebrates and in the embryos of all higher forms is represented by an elastic rod of cellular tissue enclosed in a fibrous sheath in which in higher forms cartilaginous or bony pieces develop and usually unite in various ways in the different groups to form a longitudinal series of vertebrae — compare notochord