flap vs flutter

flap and flutter both are nouns.

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

As nouns, flap and flutter are synonyms defined as:

Other synonyms of flap include flapping, fluttering.

As verbs, flutter is a hyponym of flap; that is, flutter is a word with a more specific, narrower meaning than flap:

Other hyponyms of flap include bate, clap.

flap (noun)	flutter (noun)
any broad thin and limber covering attached at one edge; hangs loose or projects freely	the act of moving back and forth
a movable airfoil that is part of an aircraft wing; used to increase lift or drag	the motion made by flapping up and down
a movable piece of tissue partly connected to the body	abnormally rapid beating of the auricles of the heart (especially in a regular rhythm); can result in heart block
the motion made by flapping up and down	a disorderly outburst or tumult
an excited state of agitation

flap (verb)	flutter (verb)
pronounce with a flap, of alveolar sounds	wink briefly
make a fuss; be agitated	beat rapidly
to flutter noisily when moved by the wind	move back and forth very rapidly
move in a wavy pattern or with a rising and falling motion	move along rapidly and lightly; skim or dart
move with a flapping motion	flap the wings rapidly or fly with flapping movements
move with a thrashing motion