The act of fluttering; quick and irregular motion.

“the flutter of a fan”

A state of agitation.

An abnormal rapid pulsation of the heart.

To flap or wave quickly but irregularly.

“flags fluttering in the wind”

Of a winged animal: to flap the wings without flying; to fly with a light flapping of the wings.

To cause something to flap.

“A bird flutters its wings.”