A mixture of feces and semen. When hardened, is stronger than diamond. Sometimes refered to as Seces.
Hobo: "My penis is covered in femen after that dirty anal sex."
Guy: "You got femen in my peanut butter."
Flatulent party Guest: "No, you got peanut butter in my femen!"
Beautiful Bridesmaid: "Wait, you're BOTH right!"
Poor Woman: "Of all the things that keep me up at night, femen is definitely the stickiest."