haymaker

Short definition from Wiktionary

Noun

1. 1
   A person or machine which harvests or prepares tall grass for use as animal fodder.
2. 2
   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
   Any decisive blow, shock, or forceful action.

Proper noun

1. 1
   A surname.