Ask FunTrivia strives to be the most accurate and complete source for answers to trivia questions on the web. Please cite all facts with citation links or references from trustable sources. Editors continuously recheck submissions and claims.
Definition of arachnoid. 1  1 : of or relating to a thin membrane of the brain and spinal cord that lies between the dura mater and the pia mater. 2  2 : covered with or composed of soft loose hairs or fibers.
Arachnoid cysts are benign cysts that occur in the cerebrospinal axis in relation to the arachnoid membrane and that do not communicate with the ventricular system.They usually contain clear, colorless fluid that is most likely normal cerebrospinal fluid; rarely, they contain xanthochromic fluid.rachnoid cysts are benign cysts that occur in the cerebrospinal axis in relation to the arachnoid membrane and that do not communicate with the ventricular system.