arachnoid vs spiderly

arachnoid is a noun but spiderly is not a noun.

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

As adjectives, arachnoid and spiderly are synonyms defined as:

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

Other synonyms of arachnoid include arachnidian, spiderlike, spidery.

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

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