Many rumors circulated on who Usher was singing about, but in an interview with The Independent On Sunday he set the record straight:

Nah, it’s not, and it’s funny because I knew that people would potentially assume that. And me and Pharrell talked about it – and he explained it to me as we were writing. ‘Nah,’ he said, ‘that’s not what it’s about, Ush.’ What it’s about is a person who is going through something that he can’t understand and can’t control this woman’s emotion. And it’s a song that actually celebrates women. Then the other side is this guy saying, ‘You gotta be twisted if you think I’m gonna accept this.’ Then there’s the triple-entendre of just a woman twisting her lipstick.

https://www.youtube.com/watch?v=NOo4hDjM2NQ