It means to be very cool, crazy, fuckin great, awesome or it can be substituted as "hell yeah".
"Man I went to a crunkin party last night...fun shit"
"Thats crunkin fo sho"
Something that is astonishing, or unbeleivable. Could relate to a party, a young woman, or a car.
"Damn girl, you're all crunkin and shit"
"See Wally's lux ride? Those hydraulics are crunkin."