BESCUMBER (v)
Definition: To spray with poo.
Analysis: Actually bescumber is just one of many words in the English language that basically mean “to spray with poo”. These are: BEDUNG, BERAY, IMMERD, SHARNY, and the good ol’ SHITTEN. In special cases, you can use BEMUTE (specifically means to drop poo on someone from great height), SHARD-BORN (born in dung), and FIMICOLOUS (living and growing on crap).
Alternative: If that is too vulgar, you can use BEVOMIT and BEPISS, which meanings should be obvious to you, as well as BESPAWL (to spit on).
Oh, and if you want to say poo without looking like you're saying it, you can use ORDURE, DEJECTION, and EXCRETA. To mean something more specific, you can use MECONIUM (first feces of a newborn child), MELAENA or MELENA (the abnormally tarry feces containing blood from gastrointestinal bleeding), LIENTERY (diarrhea with undigested or partially digested food), and STEATORRHEA (fatty stool that's hard to flush down).
NINNYHAMMER (n)
Definition: A fool or a silly person.
Analysis: The word "fool," unless you're Mr. T, is sometimes woefully inadequate to express the stupidity of the person you're talking about. So use Ninnyhammer. Or at least NINNY.
Alternative: The English language is chockful of colorful words meaning stupid person, such as: DUMMKOPF, IGNORAMUS, JOBBERNOWL, GOWK, and WITLING.
For mental retardation, eschew the ubiquitous 'tard - rather, use AMENTIA (extreme mental retardation because of inadequate brain tissue), CRETINISM (mental retardation associated with dwarfism, caused by the deficiency of a thyroid hormone, a person with cretinism is a CRETIN), and MORONITY (used to mean mild retardation of having a mental age of 7 to 12 years, now it's an obsolete term though we still use the word moron).
HIRCISMUS (n)
Definition: Offensive armpit odor.
Analysis: Hircismus comes from the root word "hircus" which means goat in Latin. Someone must have thought smelly pits smelled like goats. Actually, this word combines two sources of great insult potential: smelly and armpits. Why this is not used more often in the discourse of hateful communication is beyond me.
Alternative: As we've mentioned, armpit is an untapped goldmine for insults. Here are some examples of words you can use: MASCHALEPHIDROSIS or MASCHALYPERIDROSIS (excessive sweating of the armpits). MASCHALOPHILOUS (sexual attraction to the underarms) and AXILLISM (the use of armpit for sex).
Smelling like goats is also a good source of insults (especially since goat is also a slang for a lecherous man). Try CAPRYLIC and HIRCINE (smelling like a pungent goat), and CAPRIC (resembling a goat).