whitecap

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A wave with a crest of foam.

from The Century Dictionary.

• noun The inner chaff of wheat: chiefly in the plural.
• noun The male redstart, a bird, Ruticilla phœnicura. See first cut under redstart.
• noun The tree-or mountain-sparrow, Passer montanus.
• noun 3. plural The common mushroom, Agaricus campestris.
• noun Nautical, a wave with a broken crest showing as a white patch; a white horse.
• noun [capitalized] One of a self-constituted body or committee of persons, who, generally under the guise of rendering service or protection to the community in which they dwell, commit various outrages and lawless acts.

from the GNU version of the Collaborative International Dictionary of English.

• noun The European redstart; -- so called from its white forehead.
• noun The whitethroat; -- so called from its gray head.
• noun The European tree sparrow.
• noun A wave whose crest breaks into white foam, as when the wind is freshening.
• noun United States 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun any of several birds having a white patch on the head
• noun a wave having a white crest; a breaker

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a wave that is blown by the wind so its crest is broken and appears white