flap [flæp]

以下由轻松背单词网站提供

n.垂下物，帽沿，袋盖；v.拍打，拍动

to wave something, especially wings when or as if flying

Although I moistened it, the flap doesn't stick to the envelope. 我把信封弄湿了，可是信封口盖还是粘不上。
With a flap of its wings the sparrow flew off. 麻雀忒儿一声飞了。