1) A form of whammying on guitar hero known to get the most amount of points quickly by alternating between no whammy and fully whammy in the quickest amount of time.
2) A euphemism for tearful masterbation.
1) 'Dude, you got so many points, you must have been dan-whammying!'
2)
Person A: 'Dude, why the fuck are you crying and ejaculating on yourself?'
Person B: 'Oh, i've been Dan-Whammying.'