Eh, it depends on the intention behind the word. Narcissistic personality disorder is, by definition, a disability (as are all mental disorders). In practice, it isn't treated as such because they're just assholes. Therapy is the only treatment, and the likelihood of a narcissist actually seeking treatment is basically 0.

Most people throw the term around loosely, much like "psychopath." I'm mainly being pedantic and do agree that it is often the best word to use to describe people who exhibit narcissistic symptoms. Selfish and egotistical can be an understatement for even neurotypical people.

I'm just really interested in psychology and have a compulsion to talk about it to internet strangers who never asked and probably don't care.