Definition of plough jack in US English:

plough jack

(US plow jack)

noun

English Regional, Lincolnshire, Northern
historical
  • A mummer participating in the celebration of Plough Monday.

Origin

Mid 19th century. From plough + Jack. Slightly earlier currency is probably implied by plough jag.

Pronunciation

plough jack

/ˈplaʊ dʒak/