The Collaborative International Dictionary of English v.0.48:

Hoopoe \Hoop"oe\, Hoopoo \Hoop"oo\, n. [So called from its cry;
   cf. L. upupa, Gr. ?, D. hop, F. huppe; cf. also G.
   wiedenhopf, OHG. wituhopfo, lit., wood hopper.] (Zool.)
   A European bird of the genus Upupa (Upupa epops), having
   a beautiful crest, which it can erect or depress at pleasure,
   and a slender down-curving bill. Called also hoop, whoop.
   The name is also applied to several other species of the same
   genus and allied genera.

WordNet (r) 3.0 (2006):

hoopoo
    n 1: any of several crested Old World birds with a slender
         downward-curved bill [syn: hoopoe, hoopoo]