Nervous perspiration caused by a fear of failure before an audience.
The applause had been deafening on her entrance, but after ten minutes the air was heavy with "flop sweat".
The light and tiny beads of sweat that transfer from the back of a males scrotum to the skin of a female during sex, usually propelled by the energy of the sack flopping back and forth.
You could tell that the stain on her dress was less the usual culprit, and more flop sweat than anything else. The key was in the viscosity.