Definition of mash potato in US English:

mash potato

noun

US
  • 1Mashed potato.

  • 2Also with capital initials. = "mashed potato".

Origin

Late 18th century; earliest use found in James Woodforde (1740–1803), diarist and Church of England clergyman. Probably partly from mash + potato, and partly shortened from mashed potato.

Pronunciation

mash potato

/ˌmaʃ pəˈteɪtəʊ/