means Relating to the spine or backbone, especially the column of vertebrae that protects the central nerve cord running down your back.

from From Latin spina, "thorn, spine, backbone" — the same word for the prickle on a plant and the ridge of bone down an animal's back, the two sharing that idea of something sharp and protruding. The English adjective spinal arrived through Late Latin spinalis, and spina also gave us "spine" itself and, less obviously, "spinney," a thicket of thorny growth.