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.