farmer giles;1236172 wrote: i thought a nark was a snitch an informer a grass
i thought it was a narcotic user at worst
but it appears i was wrong some one told me what a narc means ,does any one else know this meaning
thoughts pleaase

Depends where you are does it not? If you're in the UK it is still in common parlance if you are in america they don't use the word the same way. They are speaking a different dialect from you called american english. Like their spelling it is different and only correct in an american context. Similarly with narc used in the sense of meaning a policeman on the narcotics squad. We refer to the drug squad.
Narcissistic or narcissism is a complete meaning on it's own- you don't need to add personality disorder to the word since it is in itself clear what it means. You are narcissistic is quite clear, you are suffering from narcissistic personality disorder sounds like a psychiatrist trying to pad his bill. A self obsessed individual is narcissistic, might need psychiatric help perhaps to sort themselves out but mentally ill?