n. The fore part of the night last past; the previous evening. [ R. ] Shak. [ 1913 Webster ]
adv. 1. In the fore part of the night last past; in the evening before. [ 1913 Webster ]
2. Throughout the night; as, the candle will not last overnight. [ 1913 Webster ]
3. During the night; hence, in a short period of time; as, his prospects of winning changed overnight. [ PJC ]
I had been telling her all that happened overnight. Dickens. [ 1913 Webster ]
a. Ocurring or accomplished during one night; as, guaranteed overnight delivery of a package. [ PJC ]