noun
(archaic, now only in for the nonce) The one or single occasion; the present reason or purpose.
(lexicography) A nonce word.
(cryptography) A value constructed so as to be unique to a particular message in a stream, in order to prevent replay attacks.
adjective
One-off; produced or created for a single occasion or use. Denoting something occurring once.
noun
(British, Ireland, derogatory) A sex offender, especially one who is guilty of sexual offences against children.
(by extension) A pedophile.
(British, Ireland, prison slang, derogatory) A police informer, one who betrays a criminal enterprise
(British, Ireland, slang, derogatory) A stupid or worthless person.