(die, 41 letters) "regulation requiring a prescription for an anesthetic"
(der, 30 letters) This word may be short in comparison to those below, but it's a real word submitted by Robin in our Forum, taken from a letter he received. It means roughly "head district chimney sweep."
bauunterbeamtengesellschaft (one word, no hyphen)
(die, 79 letters, 80 with new German spelling [one more 'f' in ...dampfschifffahrts...]) "association of subordinate officials of the head office management of the Danube steamboat electrical services" (the name of a pre-war club in Vienna) - Not really useful, this word is more of a desperate attempt to lengthen the word below.
(der, 42 letters) "Danube steamship company captain"
(die, plur., 39 letters) "legal protection insurance companies"
According to Guinness, this was the longest German dictionary word in everyday usage, but the word below is a longer legitimate, official "longest word" — in semi-everyday usage.
(das, 63 letters) "beef labeling regulation & delegation of supervision law"
This was a 1999 German Word of the Year, and it also won a special award as the longest German word for that year. It refers to a "law for regulating the labeling of beef" - all in one word, which is why it is so long. German also likes abbreviations, and this word has one: ReÜAÜG.
This business is well ended.
My liege, and madam, to expostulate
What majesty should be, what duty is,
Why day is day, night night, and time is time,
Were nothing but to waste night, day and time.
Therefore, since brevity is the soul of wit,
And tediousness the limbs and outward flourishes,
I will be brief: your noble son is mad:
Mad call I it; for, to define true madness,
What is't but to be nothing else but mad?
But let that go.