tapering off vs tapering

tapering off is not a noun while tapering is a noun.

Word	Noun	Adjective	Verb	Adverb
tapering off	No	Yes	No	No
tapering	Yes	Yes	No	No

As adjectives, tapering off and tapering are synonyms defined as:

Other synonyms of tapering off include dwindling.

tapering off (noun)	tapering (noun)
	the act of gradually lowering the size or amount

tapering off (adjective)	tapering (adjective)
gradually decreasing until little remains	gradually decreasing until little remains
	becoming gradually narrower