arachnoid

[uh-rak-noid]
adjective
  1. resembling a spider's web.
  2. of or belonging to the arachnids.
  3. Anatomy. of or relating to the arachnoid membrane.
  4. Botany. formed of or covered with long, delicate hairs or fibers.
noun
  1. an arachnid.
  2. Anatomy. the serous membrane forming the middle of the three coverings of the brain and spinal cord.

Origin of arachnoid

1745–55; < New Latin arachnoīdes < Greek arachnoeidḗs cobweblike. See arachnid, -oid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for arachnoid

arachnoid

noun
  1. the middle of the three membranes that cover the brain and spinal cordSee meninges
  2. another name for arachnid
adjective
  1. of or relating to the middle of the three meninges
  2. botany consisting of or covered with soft fine hairs or fibres
  3. of or relating to the arachnids
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for arachnoid
adj.

"cobweb-like," especially of the membrane around the brain and spinal cord, 1789, from Modern Latin arachnoides, from Greek arakhnoeides "cobweb-like," from arakhne "cobweb" (see arachnid) + -oeides (see -oid).

Online Etymology Dictionary, © 2010 Douglas Harper

arachnoid in Medicine

arachnoid

[ə-răknoid′]
adj.
  1. Resembling a cobweb. Used of the arachnoid membrane covering the brain and spinal cord.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

arachnoid in Science

arachnoid

[ə-răknoid′]
  1. The delicate membrane that encloses the spinal cord and brain and lies between the pia mater and dura mater.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.