What is the definition or description of: herniated disk?

See Below: A spinal disc is kind of like a jelly filled donut. The outer ring of the disc ("donut") is make up of a firm cartilage called the annulus fibrosus. The inner portion of the disc ("jelly") is called the nucleus pulposus. Over time or with trauma the annulus can eventually tear or rupture. The "jelly" in the middle of the disc can then squeeze out or "herniate" causing pain or nerve compression