If something thin or light flutters, or if you flutter it, it moves up and down or from side to side with a lot of quick, light movements.

If something light such as a small bird or a piece of paper flutters somewhere, it moves through the air with small quick movements.

If you have a flutter, you have a small bet on something such as a horse race.

If you say that someone flutters somewhere, you mean that they walk there with quick, light movements, often in a silly way or in a way which suggests that they are nervous.

If your heart or stomach flutters, you experience a strong feeling of excitement or anxiety.