arachnoid vs spidery

arachnoid is a noun but spidery is not a noun.

Word	Noun	Adjective	Verb	Adverb
arachnoid	Yes	Yes	No	No
spidery	No	Yes	No	No

As adjectives, arachnoid and spidery are synonyms defined as:

arachnoid and spidery: relating to or resembling a member of the class Arachnida

Other synonyms of arachnoid include arachnidian, spiderlike, spiderly.

arachnoid (noun)	spidery (noun)
air-breathing arthropods characterized by simple eyes and four pairs of legs
the middle of the 3 meninges

arachnoid (adjective)	spidery (adjective)
relating to or resembling a member of the class Arachnida	relating to or resembling a member of the class Arachnida