1. (使)飘动;摆动;抖搂
    If something such as a piece of cloth or paper flaps or if you flap it, it moves quickly up and down or from side to side.

    e.g. Grey sheets flapped on the clothes line...
           灰色的床单在晾衣绳上飘来摆去的。
    e.g. They would flap bath towels from their balconies as they chatted.
           他们聊天时会在阳台上抖搂浴巾。

2. 振(翅);挥(翅);(翅膀)拍打，抖动
    If a bird or insect flaps its wings or if its wings flap, the wings move quickly up and down.

    e.g. The bird flapped its wings furiously...
           鸟儿使劲地扑打着翅膀。
    e.g. A pigeon emerges, wings flapping noisily, from the tower.
           一只鸽子从塔里钻出来，扑扑地拍打着翅膀。

3. 挥动，舞动(手臂)
    If you flap your arms, you move them quickly up and down as if they were the wings of a bird.

flap在线翻译

    e.g. ...a kid running and flapping her arms.
           边跑边挥舞着手臂的小孩子

4. (布、皮等)扁平下垂物,垂下的部分
    A flap of cloth or skin, for example, is a flat piece of it that can move freely up and down or from side to side because it is held or attached by only one edge.

    e.g. He drew back the tent flap and strode out into the blizzard.
           他拉开帐篷的门帘，大步走进暴风雪中。
    e.g. ...a loose flap of skin.
           耷拉着快要掉下的一块皮

5. (飞机的)襟翼，副翼，阻力板
    A flap on the wing of an aircraft is an area along the edge of the wing that can be raised or lowered to control the movement of the aircraft.

    e.g. ...the sudden slowing as the flaps were lowered.
           襟翼放下时的突然减速

6. (鸟翼、布条、纸片的)拍打声，拍动，拍打
    A flap is a sudden noise or movement made by a bird's wing or by a piece of paper or cloth when it flaps.

    e.g. Nothing to be heard but the soft flap of a silk banner.
           万籁俱寂，只有一面绸制旗子轻轻飘动的响声。

7. 激动;焦虑;惊慌
    Someone who is in a flap is in a state of great excitement, worry, or panic.

    e.g. Why did people get in a flap over nuclear energy?...
           为什么人们对核能惶恐不安呢？
    e.g. Wherever he goes there's always a flap.
           无论他到哪里，都会引起一阵骚动。