arachnoid

[ uh-rak-noid ]

adjective

resembling a spider's web.
of or belonging to the arachnids.

Anatomy. of or relating to the arachnoid membrane.
Botany. formed of or covered with long, delicate hairs or fibers.

noun

an arachnid.
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

Compare dura mater, meninges, pia mater.

Words Nearby arachnoid

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use arachnoid in a sentence

The researchers tracked antigens and other substances crossing the arachnoid barrier, an obstacle that’s known for its impermeability but which, they found, leaks in this particular area.
A Backdoor Lets the Immune System Monitor the Brain | Elena Renken | April 28, 2021 | Quanta Magazine
He coped for two decades with headaches caused by an arachnoid cyst in his brain.
Urban Meyer returns to coaching, jumps to NFL with hiring by Jacksonville Jaguars | Mark Maske | January 15, 2021 | Washington Post
The arachnoid has also shown slight congestion, and in other cases the membranes showed a slight thickening.
Barium, A Cause of the Loco-Weed Disease | Albert Cornelius Crawford
The lymph was purely basal, solely on the arachnoid, not in the fissures or sulci.
A History of Epidemics in Britain, Volume II (of 2) | Charles Creighton
In quite young specimens the collector will notice two well defined arachnoid veils, the lower one being much more dense.
The Mushroom, Edible and Otherwise | M. E. Hard

From its resemblance to a spider's web such a veil is said to be arachnoid.
Studies of American Fungi. Mushrooms, Edible, Poisonous, etc. | George Francis Atkinson
Let them form arachnoid associations, spinsters and spiders would be a good motto.
The Poet at the Breakfast Table | Oliver Wendell Holmes, Sr.

British Dictionary definitions for arachnoid

arachnoid

/ (əˈræknɔɪd) /

noun

the middle of the three membranes that cover the brain and spinal cord: See meninges
another name for arachnid

adjective

of or relating to the middle of the three meninges
botany consisting of or covered with soft fine hairs or fibres

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

Scientific definitions for arachnoid

arachnoid

[ ə-răk′noid′ ]

The delicate membrane that encloses the spinal cord and brain and lies between the pia mater and dura mater.

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