Sentence:  “We call this getting yourself in a square corner, when you run out of ideas and experience at the same time,” said Mr. Barr, a fighter pilot in the Vietnam War. “ . . . Even for a good pilot, that could produce a <WSD>death spiral</WSD>.” 
Meaning of the word marked with <WSD> tags:  The downward, corkscrew-motion of a disabled aircraft which is unrecoverably headed for a crash.