What is Flutter ?
Flutter is (noun) 1. a light movement, especially of wings With a flutter of wings, the robin landed on the bird-table. 2. a small gamble (informal.) Sometimes I have a flutter at our local racetrack. 3. a very quick movement of the heart We detected a slight heart flutter. (verb) 1. to move wings quickly but with not a lot of force The little bird fell out of its nest and fluttered to the ground. 2. to move softly and quickly Dead leaves fluttered from the trees. The flags fluttered in the breeze.
source: Easier English, Student Dictionary Upper Intermediate Level