Term coined by Terry Pratchett in "Equal Rites", part of the Discworld series of books.
This is only pronounced by highly paid stunt linguists, and members of the K'tumi tribe.
Loosely translated, it means: The nasty sound of a sword being unsheathed right behind one at just the point when one thought all enemies had been dispatched.
It is widely agreed that this definition doesn't capture the cold, gut wrenching terror of the original one.
When your eyes fly open, your heart moves several inches up in your chest, and doubles in size, when your throat seems to be blocked with something large and painful, when you feel a sinking feeling through your whole body, knowing that the victory celebration you were looking forward to is going to be replaced by a fast death: That is p'ch'zarni'chiwkov.
P'ch'zarni'chiwkov gives recognition to a feeling commonly known but unnamed. Douglas Adams gives many more of these feelings names in The Meaning of Liff.