My South-African relatives use this term to describe a major family incident, like when somebody comes out of the closet or whatever. As in, “ach, man, when Lars announced he was marrying that stripper, it was a total rundepest. My grandmother was threatening to slit her wrists.”
It’s pronounced roon-de-pest, and is apparently not an Afrikaans word. I Googled extensively, but couldn’t turn up anything. My step-mother thought it might be Slavic or Russian. Does anybody have any ideas?
I was reminded about the term by this Neatorama post from a while back.
UPDATE: Thanks for all the tips on the, uh, cattle plague. A reader writes in with a definition from the Oxford University Press dictionary of South African English:
rinderpest: a virulent highly infectious cattle disease long known in Europe but with particular historical significance in SA where it broke out in 1896; described as the greatest shock ever sustained by the agricultural community in SA.
DarrenBarefoot.com 
Dutch for a type of cattle plague:
http://nl.wikipedia.org/wiki/Runderpest
Hmm…well, maybe it moved into slang usage from there?
Hi Darren
I am a South African living in Cape Town. I looked at the Wikipedia explanation, which is in the Dutch language and thus provides the Dutch spelling. However, in the South African Bilingual Dictionary of Bosman, Van der Merwe and Hiemstra (1984), it is spelt differently: In English it appears as ‘rinderpest’ (cattle-plague) and in Afrikaans it appears as ‘runderpes’. What you have is a combination of the two spellings, which might be why you couldn’t find anything yourself.
My husband grew up on a farm and he says it is a disease caught by horses, as far as he knows. Both of us know its meaning as a plague, but neither of us have ever heard of the way it is used by your relatives. So I deduce the following:
–that the word evolved with a special meaning in your family (which often happens in families–we also have such words that only our family members understand the special meaning of).
–that a synonym for the way your family uses it would be ‘disaster’ (in the sense that a plague is a big disaster).
Hope this helps.
As soon as I saw the explanation, I knew that indeed it is a cattle plague. Also it makes sense that it is indeed from the Dutch language. Spelling interesting. I should have known that pes is the afrikaans for pest. Good searching.
Glad to see the official explanation. Given that my family is Hungarian (your wife’s too, I assume) – I figured it was a reference to “Budapest”. Eastern Europeans are notoriously dramatic and a “major family incident” is pretty much a daily occurence.
Cattle plague, eh? Oh well, same difference.