1. A greeting to say whats up
2. A greeting to say how is your day
3. A saying to say killer, sweet or dude
4. Scratchin can be used to say a combination of the three above.
Scratchin was first heard at Peets coffee in Concord, CA, it was said by some punk kid as a greeting.
Punk Kid: Whats scratchin
Robin: nothing much
Robin: What's good?
Punk Kid 2: OMFG I had a scratchin day!