flutter vs nictitate

flutter is a noun but nictitate is not a noun.

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

As verbs, nictitate is a hypernym of flutter; that is, nictitate is a word with a broader meaning than flutter:

Other hypernyms of flutter include blink, nictate, wink.

flutter (noun)	nictitate (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)	nictitate (verb)
wink briefly	briefly shut the eyes
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