A*rach"noid (&?;), a. [Gr. &?; like a cobweb; &?; spider, spider's web + &?; form.] 1. Resembling a spider's web; cobweblike.

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

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

A*rach"noid, n. 1. (Anat.) The arachnoid membrane.

2. (Zoöl.) One of the Arachnoidea.