Chrunk means, get excited, get hype or have some fun. It can be used a little different, but that is the general idea.
It is a largely a southern slang term, used in the hip hop community or people familiar with urban culture to describe a feeling like "Woodee." I have a cousin that lives in Atlanta and travels to Chicago on business a few times a year and he used that term quite often at times or at least did. And I have family that live in Miami and they used it as well.
I knew someone was going to ask this question.
Peace