stick-in-the-mud vs slowpoke

stick-in-the-mud and slowpoke both are nouns.

Word	Noun	Adjective	Verb	Adverb
stick-in-the-mud	Yes	Yes	No	No
slowpoke	Yes	No	No	No

As nouns, stick-in-the-mud and slowpoke are synonyms defined as:

Other synonyms of stick-in-the-mud include plodder, slowcoach.

stick-in-the-mud (noun)	slowpoke (noun)
someone who moves slowly	someone who moves slowly

stick-in-the-mud (adjective)	slowpoke (adjective)
(used pejoratively) out of fashion; old fashioned