To boogie or dance and usually jump enthusiastically around whilst listening to J-Pop or Japanese pop music.
Usually includes the dancer singing what little of the Japanese lyrics they know along with the song, and inevitably singing the English the artist includes as it's the only part they honestly understand.
Though J-Popping is mostly done by Japanese fangirls (though who love everything Japanese, purely because it's Japanese), it is also done by anyone with a passion for happy, energetic music.
Kid 1: "what is that kid doing under there?"
kid 2: "I don't know, looks like he's digging deep in his pocket for something."
kid 1: " no, i think he's j pocketing."