The definition of subarachnoid is the space between the brain and the membranes that cover the brain and spinal cord.
An example of subarachnoid is a loss of blood from a ruptured blood vessel just under the membrane that covers the brain.
located in the space between the arachnoid and the pia mater membranes of the brain and spinal cord, which contains cerebrospinal fluid: a subarachnoid hemorrhage
Origin of subarachnoidsub- + arachnoid
Situated or occurring beneath the arachnoid membrane, or between the arachnoid and the pia mater: subarachnoid hemorrhage.
- (medicine) Located or occurring below the arachnoid mater, often specifically between the arachnoid membrane and the pia mater
sub- +"Ž arachnoid