*knock² n [C] 1 the sound of someone or something hitting a hard surface 敲击声: There was a loud knock at the door. 传来一下很响的敲门声。 2 when something hits something else, especially in a way that causes damage or injury 〔尤指造成损毁或损伤的〕敲击; 撞击: a knock on the head 头上被撞了一下