A scrub but with a k (skrub) is a sophisticated word that you use on the low of the low. They have to be a scab and annoy the f*ck out of you.
Example
Cooper: can i have 2$
You: sure
Cooper:
ill pay you back tommorrow
1 Month later
You: just give me my f***ing
money.
Cooper:
mum they're bullying me.
Moral of the story dont be a cooper.