In the fore part of the night last past; in the evening before; also, during the night; as, the candle will not last overnight
You can say that something happens overnight when it happens very quickly and unexpectedly. The rules are not going to change overnight Almost overnight, she had aged ten years and become fat. Overnight is also an adjective. In 1970 he became an overnight success in America
happening in a short time or with great speed; "these solutions cannot be found overnight!"
If you overnight somewhere, you spend the night there. They had told her she would be overnighting in Sydney. Overnight is also a noun. Overnights can be arranged