Raining cat and dog什麼意思

"Raining cats and dogs" is an English idiom that means it is raining extremely heavily. It is often used to describe a downpour, where the rain is falling so heavily and continuously that it seems almost impossible to go outside. The origin of this idiom is not definitively known, but it has been in use since at least the 17th century. Some believe it may have originated from the fact that during heavy rains, animals such as cats and dogs would sometimes get swept up in the storm and end up floating in the streets, giving the appearance of raining animals. However, this is likely a folk tale and there are other theories about the origin of the phrase.