arachnoid

1 of 3

adjective (1)

arach·​noid ə-ˈrak-ˌnȯid How to pronounce arachnoid (audio)
1
: of or relating to a thin membrane of the brain and spinal cord that lies between the dura mater and the pia mater
2
: covered with or composed of soft loose hairs or fibers

arachnoid

2 of 3

noun

: an arachnoid membrane

arachnoid

3 of 3

adjective (2)

: resembling or related to the arachnids

Examples of arachnoid in a Sentence

Recent Examples on the Web
Adjective
Since then, the arachnoid warrior (voiced by Shameik Moore) has grown into his powers and superhero responsibilities. Lovia Gyarkye, The Hollywood Reporter, 31 May 2023
Noun
At Children's Minnesota, Dr. Kyle Halvorson said arachnoid cysts are more commonly found in a patient's head, but rarely by the spinal column. Kelly Smith, Star Tribune, 24 Mar. 2021 In 2018, Meyer retired from the Ohio State job, citing health concerns, including headaches related to a congenital arachnoid cyst. New York Times, 14 Jan. 2021

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'arachnoid.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

Noun

New Latin arachnoides, from Greek arachnoeidēs, like a cobweb, from arachnē spiderweb

Adjective (2)

New Latin Arachnida + English -oid

First Known Use

Adjective (1)

1789, in the meaning defined at sense 1

Noun

1804, in the meaning defined above

Adjective (2)

1825, in the meaning defined above

Time Traveler
The first known use of arachnoid was in 1789

Dictionary Entries Near arachnoid

Cite this Entry

“Arachnoid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/arachnoid. Accessed 28 Mar. 2024.

Medical Definition

arachnoid

1 of 2 noun
arach·​noid ə-ˈrak-ˌnȯid How to pronounce arachnoid (audio)
: a thin membrane of the brain and spinal cord that lies between the dura mater and the pia mater

arachnoid

2 of 2 adjective
variants also arachnoidal
: of or relating to the arachnoid
the arachnoid membrane
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