fluttering vs flutter

fluttering and flutter both are nouns.

Word	Noun	Adjective	Verb	Adverb
fluttering	Yes	No	No	No
flutter	Yes	No	Yes	No

As nouns, fluttering and flutter are synonyms defined as:

Other synonyms of fluttering include flap, flapping.

fluttering (noun)	flutter (noun)
the motion made by flapping up and down	the act of moving back and forth
	the motion made by flapping up and down
	abnormally rapid beating of the auricles of the heart (especially in a regular rhythm); can result in heart block
	a disorderly outburst or tumult

fluttering (verb)	flutter (verb)
	wink briefly
	beat rapidly
	move back and forth very rapidly
	move along rapidly and lightly; skim or dart
	flap the wings rapidly or fly with flapping movements