adjective

1. Anatomy. Of or relating to a delicate membrane enclosing the spinal cord and brain.
2. Of, relating to, or resembling arachnids.
3. Covered with or consisting of thin, soft, entangled hairs or fibers resembling those of a cobweb or spider's web.

noun

1. See ARACHNID.
2. Anatomy. A delicate membrane that encloses the spinal cord and brain, and lies between the pia mater and dura mater.

[New Latin arachnoidês, from Greek arakhnoeidês, cobweblike : arakhnê, spider + -oeidês, -oid.]

The American Heritage® Dictionary of the English Language, Third Edition copyright © 1992 by Houghton Mifflin Company. Electronic version licensed from InfoSoft International, Inc. All rights reserved.