flutter

Short definition from Wiktionary

Verb

1. 1
   To flap or wave quickly but irregularly.
2. 2
   Of a winged animal: to flap the wings without flying; to fly with a light flapping of the wings.
3. 3
   To undergo divergent oscillations (potentially to the point of causing structural failure) due to a positive feedback loop between elastic deformation and aerodynamic forces.
4. 4
   To cause something to flap.
5. 5
   To drive into disorder; to throw into confusion.
6. 6
   To be in a state of agitation or uncertainty.
7. 7
   To be frivolous.
8. 8
   To subject to a lie detector test.

Noun

1. 1
   The act of fluttering; quick and irregular motion.
2. 2
   A state of agitation.
3. 3
   An abnormal rapid pulsation of the heart.
4. 4
   An extremely dangerous divergent oscillation caused by a positive feedback loop between the elastic deformation of an object and the aerodynamic forces acting on it, potentially resulting in rapid structural failure.
5. 5
   A small bet or risky investment.
6. 6
   A hasty game of cards or similar.
7. 7
   The rapid variation of signal parameters, such as amplitude, phase, and frequency.