Draco caught sight of Harry, Ron, Hermione and Ginny staring at him, nodded curtly and shouted "what yo' mudblood asses doin' starin' at me mugglefuckers!"
A term originated in the furry fandom. It means someone with a short penis. The word came from the thought that anthro creatures, such as wolves, have a long muzzle. If you can get past the muzzle with a blowjob, you are okay. If you can't make it (past the muzzle), you are a muzzle fucker.
"Did you hear what <asshole person> did to my car window? That Muzzle Fucker threw a rock through it!"
A person of less expertise, experience, knowledge, and understanding that causes great frustration to someone with greater knowledge, experience and expertise.
Sticking your hand up a girl's anus, as in fisting, and you grab onto her intestines and pull them out. People who do this are called Dutch Munklefuckers.
"Dude I stuck my hand in my girlfriend's ass and pulled her innards out! It was hot!"
"DUDE! You're such a Dutch Munklefucker!"