Dirty Mallard 

A sexual act performed when a male, while having sex with a female in either the missionary or more preferably the doggy style position, reaches around his backside and obtains a sizeable amount of sweat from his Perineum (a.k.a. Chode, Brum, Taint, etc.). Said sweat is then wiped upon the females upper lip, directly underneath the nose. The maneuver is completed with the male folding each of his arms to resemble wings, flapping his "wings", and vocalizing an ear-shattering "Quack-Quack".

As Brian was ravishing Krista from the rear and giving her the ultimate in sexual pleasure, Krista suddenly felt Brians finger on her upper lip. Within an instant her olfactory senses were overwhelmed by an extremely foul odor, accompanied by the loud call of the Mallard Duck and a rush of air upon her backside presumably caused by the flapping of limbs. Unbeknownst to Krista, she had received the ultimate sexual insult: The Dirty Mallard!

Dirty Mallard by Landon M. September 28, 2006

dirty mallard 

the act of scraping some duck butter from your grundle
and smearing it on one's face, often under the nose and above the lip, like a dirty sanchez

Joe: what's that on your face?

Bob: that nasty fuck over there just gave me a dirty mallard

Joe:....tisfu

dirty mallard by Blake C. June 16, 2008