NPD does. The dsm-iv diagnosis of narcissistic personality disorder (npd) does, more info here: http://www.Behavenet.Com/narcissistic-personality-disorder. But narcissism is used as an everyday, non-psychiatric label too. In an informal sense it may mean someone who is self-important or too proud of themselves. Many psych terms have a technical meaning and are used in casual speech too.
Yes. Consult the dsm 4 criteria for it online (google it?) it is self-explanatory, and very simple to determine.
Narcissism. The hallmark of a narcissist is an immense ego, grandiosity, and self-importance, as well as being entitled, and a tendency to use and objectify others as well as thinking of people in all-good or all-bad terms instead of shades of gray. The core of a narcissist is profound insecurity.