tightly fitting vs skinny

tightly fitting is not a noun while skinny is a noun.

Word	Noun	Adjective	Verb	Adverb
tightly fitting	No	Yes	No	No
skinny	Yes	Yes	No	No

As adjectives, tightly fitting and skinny are synonyms defined as:

Other synonyms of tightly fitting include tight-fitting, tight fitting, tightfitting.

tightly fitting (noun)	skinny (noun)
	confidential information about a topic or person

tightly fitting (adjective)	skinny (adjective)
fitting snugly	of or relating to or resembling skin
	giving or spending with reluctance
	being very thin
	fitting snugly