To wave or flap rapidly in an irregular manner: curtains that fluttered in the breeze. To fly by a quick light flapping of the wings. To flap the wings without flying. To move or fall in a manner suggestive of tremulous flight: "Her arms rose, fell, and fluttered with the rhythm of the song\u201d ( Evelyn Waugh). To vibrate or beat rapidly or erratically: My heart fluttered wildly. To move quickly in a nervous, restless, or excited fashion; flit. To cause to flutter: "fluttering her bristly black lashes as swiftly as butterflies' wings\u201d ( Margaret Mitchell). The act of fluttering. A condition of nervous excitement or agitation: Everyone was in a flutter over the news that the director was resigning. A commotion; a stir. Pathology Abnormally rapid pulsation, especially of the atria or ventricles of the heart. Rapid fluctuation in the pitch of a sound reproduction resulting from variations in the speed of the recording or reproducing equipment. Chiefly British A small bet; a gamble: "If they like a flutter, Rick will get them better odds than the bookies\u201d ( John le Carr\u00e9).