cerebrospinal fluid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The serumlike fluid that circulates through the ventricles of the brain, the cavity of the spinal cord, and the subarachnoid space, functioning in shock absorption.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun medicine Abbreviated CSF. A clear bodily fluid in the form of a very pure saline solution with microglia that occupies the subarachnoid space in the brain (between the skull and the cerebral cortex), and which acts as a cushion or buffer for the cortex.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun clear liquid produced in the ventricles of the brain; fills and protects cavities in the brain and spinal cord