Nubber is actually older than any of these previous definitions. It was invented in Belper, Derbyshire, UK sometime in the 1980's, possibly the
late 1970's.
It is used to describe a particular person who has
done something a bit dodgy, like nicking a fag end from an ashtray or just being generally trampy.
It's not as specific as
Pikey, but has similar connotations.
It was also used in shouting competitions, where one person in the group would call somebody a Nubber and they would be answered with, "Did you just call me a NUBBER!" until it ended up whoever could scream it the loudest got mucho Kudos.