The act of fluttering; quick and irregular motion.

A state of agitation.

An abnormal rapid pulsation of the heart.

(uncountable, aerodynamics) 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.

(Britain) A small bet or risky investment.

A hasty game of cards or similar.

(audio, electronics) The rapid variation of signal parameters, such as amplitude, phase, and frequency.

(intransitive) To flap or wave quickly but irregularly.

(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.

(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.