The Collaborative International Dictionary of English v.0.48:

Hoop \Hoop\, v. i. [OE. houpen; cf. F. houper to hoop, to shout;
   -- a hunting term, prob. fr. houp, an interj. used in
   calling. Cf. Whoop.]
   1. To utter a loud cry, or a sound imitative of the word, by
      way of call or pursuit; to shout. [Usually written
      whoop.]
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   2. To whoop, as in whooping cough. See Whoop.
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   Hooping cough. (Med.) See Whooping cough.
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