Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Anatomy Of or relating to a delicate membrane enclosing the spinal cord and brain.
  • adjective Of, relating to, or resembling arachnids.
  • adjective Covered with or consisting of thin, soft, entangled hairs or fibers resembling those of a cobweb or spider's web.
  • noun An arachnid.
  • noun Anatomy A delicate membrane that encloses the spinal cord and brain and lies between the pia mater and dura mater.

from The Century Dictionary.

  • Of or pertaining to the Arachnida; arachnidan.
  • Like or likened to a cobweb: applied, in anatomy— to the arachnoid of the brain (see II.);
  • to the hyaloid membrane or arachnoid of the eye (see II.).
  • noun A kind of fossil madrepore.
  • noun In anatomy, the serous membrane enveloping the brain and spinal cord; the middle one of the three cerebrospinal meninges, between the dura mater and the pia mater.
  • noun An old and disused name of the hyaline or hyaloid membrane within the eyeball, especially of that portion of it which contributes to form the capsule of the crystalline lens.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Anat.) The arachnoid membrane.
  • noun (Zoöl.) One of the Arachnoidea.
  • adjective Resembling a spider's web; cobweblike.
  • adjective (Anat.) Pertaining to a thin membrane of the brain and spinal cord, between the dura mater and pia mater.
  • adjective (Bot.) Covered with, or composed of, soft, loose hairs or fibers, so as to resemble a cobweb; cobwebby.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective Relating to spiders.
  • adjective Relating to or resembling spider webs.
  • adjective anatomy Relating to the arachnoid mater, the middle layer of the meninges, the three membranes that protect the brain.
  • noun biology An arachnid
  • noun physiology The arachnoid mater, the middle layer of the meninges, the three membranes that protect the brain
  • noun astronomy A round network of fractures in the crust of Venus

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun air-breathing arthropods characterized by simple eyes and four pairs of legs
  • noun the middle of the 3 meninges
  • adjective relating to or resembling a member of the class Arachnida

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[New Latin arachnoīdēs, from Greek arakhnoeidēs, cobweblike : arakhnē, spider + -oeidēs, -oid.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

Ancient Greek ἀράχνη ("spider") + -oid

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Examples

  • The inflammation results in thickening of the middle membrane, called the arachnoid, causing it to adhere to structures near it.

    Glaxo, Myodil and The UK Regulator 2008

  • In the arachnoid membrane are small areas called arachnoid villi (vil'eye; "tufts of hair" L, so named because they have the appearance of tiny tufts).

    The Human Brain Asimov, Isaac 1963

  • The arachnoid is a thin membrane which lies beneath the dura mater.

    A Practical Physiology Albert F. Blaisdell

  • Finally, within the spaces of the arachnoid is a lymph-like liquid which completely envelops the brain and the cord, and which, by serving as a watery cushion, protects them from jars and shocks.

    Physiology and Hygiene for Secondary Schools Francis M. Walters

  • The Arachnoid—The arachnoid is a delicate membrane enveloping the brain and medulla spinalis and lying between the pia mater internally and the dura mater externally; it is separated from the pia mater by the subarachnoid cavity, which is filled with cerebrospinal fluid.

    IX. Neurology. 4g. The Meninges of the Brain and Medulla Spinalis 1918

  • The Spinal Part (arachnoidea spinalis) of the arachnoid is a thin, delicate, tubular membrane loosely investing the medulla spinalis.

    IX. Neurology. 4g. The Meninges of the Brain and Medulla Spinalis 1918

  • The arachnoid is a thin, transparent sheath, separated from the pia mater by a comparatively wide interval, the subarachnoid cavity, which is filled with cerebrospinal fluid.

    IX. Neurology. 3. The Spinal Cord or Medulla Spinalis 1918

  • It’s blood pooling between the dura that covers the brain and the arachnoid, which is the middle layer of the meninges.

    HOUSE RULES JODI PICOULT 2010

  • Just now, as he watched his sister pirouette in and out of frame, a little brown arachnoid was spinning the finishing touches on a window-spanner.

    Charles Watches Georgina and Tries Not To Feel "The Creep." Laurence Wilhelm Lillvik 2011

  • Last month, Sports Illustrated chronicled Meyer's coaching career and reported that he suffered from persistent headaches caused by an arachnoid cyst that becomes inflamed by stress, rage and excitement.

    Urban Meyer To Resign: Health Concerns Push Florida Football Coach To Quit The Huffington Post News Team 2009

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