A terrible misspelling of the word “nonce” which is an acronym used in British prisons for “not on normal courtyard exercise.” Usually used to refer to sex offenders or anyone that’s not allowed in general.
Noun: what you say when trying to recount when an event occurred, only to realise that it never actually has. Much like once, twice or thrice, but meaning never, or zero times.
A: "How many times do I have to tell you to slow down before I kick your ass?"
B: "... Nunce."