white·cap /ˈhwaɪtˌkæp, ˈwaɪt-/
  白頭巾團員
  White·cap n.
  1. Zool. (a) The European redstart; -- so called from its white forehead.  (b) The whitethroat; -- so called from its gray head.  (c) The European tree sparrow.
  2. A wave whose crest breaks into white foam, as when the wind is freshening.
  3. A member of a self-appointed vigilance committee attempting by lynch-law methods to drive away or coerce persons obnoxious to it. Some early ones wore white hoods or masks. [U. S.] -- White*cap, v. -- White*cap*per n.
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  whitecap
       n : a wave that is blown by the wind so its crest is broken and
           appears white [syn: white horse]