arachnoid vs spiderlike

arachnoid is a noun but spiderlike is not a noun.

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

As adjectives, arachnoid and spiderlike are synonyms defined as:

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

Other synonyms of arachnoid include arachnidian, spiderly, spidery.

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

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