When a group of three to five individuals jump someone, knock them down, and proceed to violently kick them in the ribs and face repeatedly (usually with steel-toed or reinforced toe boots). Usually done while belting out lines from the popular song, "Singing In The Rain". Inspired by Stanley Kubrick's film A Clockwork Orange.
Let's take down Jake tonight. That motherfucker, we'll be singing in the rain over his ass!