ummuk'

Arabic for "your mom". Pronounced OOM-mook.
From Umm' meaning mother, and the suffix -uki (for males) or -uka (for females) for second person possesive; for ease the suffix is shortened to -uk'.

Can be used as a retort when some Arab/muslim guy is ranting. Since you can never ever say anything about their moms, it will piss them off immensly, but that's not really your concern.