1. artery or vein or vertebra situated in the lumbar region. of the loin or loins, pertaining to the part of the body below the ribs and above the hipbones (in humans or quadruped animals). lumbarartery one of four or five pairs of arteries that originate in the abdominal aorta and supply the lumbar vertebrae and the back muscles and abdominal wall [syn: arteria lumbalis]