Noun | 1. | cerebrospinal fluid - clear liquid produced in the ventricles of the brain; fills and protects cavities in the brain and spinal cord ventricle - one of four connected cavities in the brain; is continuous with the central canal of the spinal cord and contains cerebrospinal fluid medulla spinalis, spinal cord - a major part of the central nervous system which conducts sensory and motor nerve impulses to and from the brain; a long tubelike structure extending from the base of the brain through the vertebral canal to the upper lumbar region |