Defining what narcissism is, that can be tricky because as it stands there really is no cut and dry definition besides excessive self-love and a total lack of empathy. There's nothing but controversy about what causes it, nature VS nurture blah blah blah.

But I can sure as **** tell people what narcissism is NOT(though some of these may be features of some Narcissists it's not about the condition of pathological Narcissism aka NPD in and of itself):

-Vanity
-Sadism
-Psychopathy
-Sociopathy
-Vindictiveness
-Vengeful behavior
-Pathological lying
-A result of bad parenting
-A result of "ego shattering"
-Some BS defense mechanism against shame
-Some nonsense about secretly being a ray of empathetic light deep down if only someone could love a Narcissist unconditionally.