When you get a girl sopping wet and leave her hanging. Her vagina juice eventually evaporates into a horny mist leaving moisture on her inner thighs.
Frank : “Bro, I got her so worked up I could feel the vag mist”
Dave: Vag mist?
Jarret: Vag mist!?
Frank: Yeah...vag mist!!
Dave & Jarret: Not my problem.