What is the definition or description of: lumbar?

Low back: The lumbar part of the spine is the low back. It is made up of five bones (most of the time) stacked one on top of the other. They are connected by disks, facet joints, and ligaments. These soft parts allow for movement controlled by the spinal muscles; the muscles can also keep it stiff when need be. The lumbar spine also contains and protects nerves to and from the legs.

Lumbar.: Refers to something related to the area about the lower part of the spine and surrounding musculature.