Knock For A Loop Meaning

(transitive, idiomatic) To astonish; to stagger or overwhelm; to confuse or disorient.

Example: 1967 Nov. 17, "Wall Street: Big Casino," Time (retrieved 2 Aug 2014):
  [A] triple threat to the U.S. economy . . . has knocked stock prices for a loop.
1990, John Updike, Rabbit at Rest, ISBN 9780394588155, p. 394 (Google preview):
  Poor Janice, she'll be knocked for a loop. She'll feel she's let her father down.
2008 Sept. 7, Anita Gates, "Stage: Dinner and a Show, in One Spot, at One Price," New York Times (retrieved 2 Aug 2014):
  Karyn McNay as Ulla, the sexy Swedish actress/receptionist/cleaning woman, knocks the audience for a loop too.