Nonce

A nonce, in information technology, is a number generated for a specific use, such as session authentication. In this context, "nonce" stands for "number used once" or "number once."


Typically, a nonce is some value that varies with time, although a very large random number is sometimes used. A nonce can be a time stamp, a visit counter on a Web page, or a special marker intended to limit or prevent the unauthorized replay or reproduction of a file.


http://searchsecurity.techtarget.com/definition/nonce