When a man (or woman) performs cunnilingus on a woman and she farts directly in his/her face.
"I'm good at cunnilingus, but Stacy is a master of fumilingus."
Much akin to the Dirty Sanchez, a time honored event in which, while laying the bone doggy-style you insert a finger in her starfish, pull it out and wipe it across her upper lip, leaving a thin moustache. At the same time you pull her hair tightly back from her forehead, making her look like Erroll Flynn!
"I turned Dixie into Erroll Flynn last night."