If you call Britney Spears a "fat b****" while she's live on stage, it's her prerogative to respond in kind.
The 33-year-old dropped an F-bomb - and an A-bomb - at a man after he heckled her during her Piece Of Me show at Planet Hollywood in Las Vegas.
An Instagram clip uploaded by an audience member shows the moment the singer responded to the barb.
In the video Spears can be seen talking the crowd, who cheer just as the music for Till The World Ends starts up.
She turns to walk away to begin the routine, when someone beside the stage reportedly shouts "Fat B****!", although this can't be heard on the clip.