The term 'lumbar' refers to the lower BACK region of the spine. It is composed of five vertebrae, which are the largest and strongest in the spine. The term 'lumbar' is derived from the Latin word for 'LOIN, ' which is the area of the body between the ribs and hips. The lumbar region is responsible for supporting the weight of the upper body and providing flexibility and stability to the spine. The crossword solution for the term 'lumbar' is 'BACK, ' which is an accurate description of the area of the body that it refers to.