noun. A motor scooter; a motherfather; a mammy-jammer; a mama-yama. Also, a muh-fuh.
Real citation: "This big sucker will take a massive beating and still throw balls of green plasma at you that melt your skin off. While not necessarily a boss character, the Hell Knight is a badass that needs dealing with and is going to give you that action rush you’re looking for. Then a little later on you encounter the first mini boss, which is like twelve Hell Knights in one massive badass mother-you-know-what-er. Then, boom! you’ve got a boatload of action in one not-so-small package. And it’s most likely going to take you a couple tries until you defeat that big boss, even the not-quite-a-boss Hell Knight."
(Nov. 12, 2007, Planet Half-life, http://planethalflife.gamespy.com/View.php?view=Editorials.Detail&id=26)
Made-up citation: "Ooh, you're a dirty mother-you-know-what-er, Edwin! I trusted you with two things: my badger and my heart. Now I am nothing; I am rubble! Rubble!"