Reaming a dude from behind (doggy-style) and then rimming his asshole with your finger with which you run it (fecal matter and all) under his nose as to make a moustache with. Similar to the Dirty Sanchez, except strictly male related.
Is when someone else left the shop bathroom in such a stench and mess, you go into the closed down office ladies room and drop a deuce in a toilet that's been turned off because of a broken pipe.
Worker 1: You went in the girls room up front? That's been closed for six months because of that broken pipe!
Worker 2: Well now their not using it for at least a year after I dropped that dirty fergie "office style" on them!
The act of blowing air into your girlfriend's vagina, then fucking her doggie style while she queefs all over your dick. When the queefing stops, withdraw and blow more air into the vagina. Repeat until you bust a load. Then suck the load out of her vagina, spin her around, stick a straw in your mouth, and blow the gum all over her face. That is a Dirty Fergal.
*At a restaurant
Waitress: "Would you like a straw with your Coke?"
Man: "Yes please, I'm going to give this bitch a major Dirty Fergal when we get.home."