(1):

(n.) One of the Arachnoidea.

(2):

(a.) Resembling a spider's web; cobweblike.

(3):

(a.) Covered with, or composed of, soft, loose hairs or fibers, so as to resemble a cobweb; cobwebby.

(4):

(a.) Pertaining to a thin membrane of the brain and spinal cord, between the dura mater and pia mater.

(5):

(n.) The arachnoid membrane.