Scrub is a very broad term that can be used as an insult or a compliment or just a word. It is the root of Scrubjumper.
Examples[]
A: Hey do you know Cubit? B: Yeah, he's a scrub.
A: Hey scrub!
A: What a scrub!
A: Stop scrubbin around(verb)
A: Scrub me sideways(cat)