flutter vs flitter

flutter is a noun but flitter is not a noun.

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

As verbs, flutter and flitter are synonyms defined as:

Other synonyms of flutter include flicker, quiver, waver.

flutter (noun)	flitter (noun)
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

flutter (verb)	flitter (verb)
wink briefly	move back and forth very rapidly
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