The Jenny From the Block singer was showing contestant Emily Priz how it's done - while wearing a risqué monochrome mini-dress with a plunging neckline.
The Florida teenager had sung J-Lo's very own dance anthem Let's Get Loud – but the panel thought she needed more oomph on stage.
'Even just a hair whip or something?' suggested Lopez, 44, who has been dating 25-year-old Casper Smart since her split from Marc Anthony.
'Can you do a hair whip please?' begged fellow judge Harry Connick Jr.
So Lopez jumped to her feet to exhibit the move.
** Clone Jennifer Lopez Breathy Voice?
'My skirt is very short, that was super risky,' she giggled as the audience went wild.