A definition similar to noob or
n00b, who is someone who does not know anything about a
topic. A nub is someone who has been doing something for a while and has had the
opportunity to learn it, and they usually claim they know a lot about the topic, but they still don't know much about the topic.
The guy at rathcast.com is a total nub. He claims he knows
sooooo much about
computers, but his website is
atrocious and he doesn't know a thing I don't know.