Enlightenment is not what it appears to be. You can't say anything about it and try to define it without basically being incorrect. It's similar to trying to explain Zen in concrete language. If you do, you miss the point.
"Those who know don't talk, those who talk don't know." <- this is also pretty much the same thing.
It's about taking action and becoming something as opposed to talking about it.
It could also mean that if you see someone claiming to be enlightened, kill him (ignore him, be wary of him) because anyone who would claim such is probably not really enlightened.
That's my interpretation of the quote; but my interpretation means nothing.
What is more important, is what does the quote mean to YOU
P.S. please also enjoy this site
as well as Siji Tzu
. Both these sites deal pretty heavily with the subject of enlightenment.