A flutter is when something shakes or trembles quickly and lightly. It's often used to describe movement that's not too serious.
When we talk about a flutter, it usually means something small and light is moving around. For example, if you see birds flying in the sky and their wings are shaking back and forth really fast, they're probably giving you a good show of fluttering. But flutter can also be used to describe how someone feels - like when your heart starts beating quickly or you get butterflies in your stomach, which might feel like a flutter inside.
How common is "flutter"?
Word flutter is considered uncommon in modern English. It appears most frequently in fiction texts and less often in other writings.
Definitions
verb
(intransitive) To flap or wave quickly but irregularly.
Example: flags fluttering in the wind
(intransitive) Of a winged animal: to flap the wings without flying; to fly with a light flapping of the wings.
(intransitive, aerodynamics) To undergo divergent oscillations (potentially to the point of causing structural failure) due to a positive feedback loop between elastic deformation and aerodynamic forces.
(transitive) To cause something to flap.
Example: A bird flutters its wings.
(transitive) To drive into disorder; to throw into confusion.
(intransitive) To be in a state of agitation or uncertainty.
(intransitive, obsolete) To be frivolous.
(espionage, slang) To subject to a lie detector test.