Whitecap
Whitecap , noun
1.
(a) (Zoology) The European redstart; -- so called from its white forehead.
(b)
(Zoology) The whitethroat; -- so called from its gray head.
(c)
(Zoology) 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. [United States]