haymaker

/HH EY1 M EY0 K ER0/
noun
  1. 1

    A person or machine which harvests or prepares tall grass for use as animal fodder.

  2. 2

    (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.

  3. 3

    (by extension) Any decisive blow, shock, or forceful action.

Source: https://en.wiktionary.org/wiki/haymaker