What is it? Definitions Merriam-Webster Dictionary Definition: Any of various degenerative diseases of the spine. thefreedictionary.com: Degeneration of the spinal column, especially a fusion and immobilization of the vertebral bones. The term is used by many medical professionals as a synonym for spinal osteoarthritis and more specifically, for spondyloarthropathy. In this article, my aim is to focus on arthritis (arthrosis) involving the zygophyseal joints of the spine. At