mossy vs stick-in-the-mud

mossy is not a noun while stick-in-the-mud is a noun.

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

As adjectives, mossy and stick-in-the-mud are synonyms defined as:

mossy and stick-in-the-mud: (used pejoratively) out of fashion; old fashioned

Other synonyms of mossy include fogyish, moss-grown, stodgy.

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

mossy (adjective)	stick-in-the-mud (adjective)
overgrown with moss	(used pejoratively) out of fashion; old fashioned
(used pejoratively) out of fashion; old fashioned