After arousing your girlfriends sexual interests, you forcibly shove half of your clenched fist up her ass (hence the "quarter", since a "full" would be both fists), whilst simultaneously ejaculating into her anus.
The quarter pounder with cheese:

Bob: Once I got Harriet in the mood, I gave her the ol' "quarter pounder with cheese" to liven things up a little!

Doug: Sick!
by Illuminati Man March 23, 2010
An Ethopian with a yeast infection.
-How do you kill 200 flies at once?
-Hit a quarter pounder with cheese in the face.
by GuidoPosse69 February 21, 2005
an anorexic slapper with mushrooms growing out of her cabbage patch snatch
"man that was the cheesest burger i ever have eater, way better than maccas quarter punder with cheese
by matt July 26, 2003