n. A sex offender, especially of children; a paedophile.n. A stupid or worthless person.n. A datum constructed so as to be unique to a particular message in a stream, in order to prevent replay attacks.n. In a security engineering context, a value used only once.n. The one or single occasion; the present reason or purpose (now only in for the nonce).n. A nonce word.n. A number, usually generated randomly or from the time, used once in a cryptographic protocol, to prevent replay attacks.adj. denoting something occurring once.