A layer of semen on a girl's face in areas where facial hair is commonly found on men, e.g. chin, upper lip, cheeks, neck. Usually results after a blowjob.
"Do you want a blowjob, sweetheart?"
"Yeah! How do you want it to end today, honey?"
"I'd love to have a Merlin's Beard, but whatever you want. It's your special day."
"You want it, you got it!"