haymaker

1. (agriculture) A person or machine which harvests or prepares tall grass for use as animal fodder.Examples: "A long rank of haymakers—men and women—proceeded with their rakes, the white shirt-sleeves, straw bonnets, and ruddy faces, radiant in the bath of sunshine."

2. (informal, fisticuffs) A particularly powerful punch, especially one which knocks down an opponent, thrown like a scythe chop for cutting hay, as agricultural haymakers used to have strong arms.Examples: "The saga of Newt Gingrich's ethics suddenly resembles a brawl between blindfolded boxers who flail away so wildly that each lands a haymaker on his own jaw."informal

3. (figuratively, by extension) Any decisive blow, shock, or forceful action.Examples: "The real potential haymaker for the industry is a proposal, now gaining support in Congress, that would tax the profits private equity reaps on selling companies not at the low cap gains rate, but at the regular income tax rate."broadlyfiguratively