Green’s Dictionary of Slang

1. spending money recklessly and enthusiastically.

2002

‘Touré’ Portable Promised Land (ms.) 158: We Words (My Favorite Things) [...] On and poppin. Pop that junk. Don’t go there.

2. a style of street dancing involving rhythmic clenching and unclenching of muscles.

2008

‘Grandmaster Flash’ Adventures 47: Folks from four to forty, sweating and bouncing, breakin' and popping, doing the pancake and getting buck wild.