Definition of Roman punch in English:

Roman punch

noun

historical
  • A drink consisting of a semi-frozen mixture of sugar, water, lemon juice, and various spirits (the original recipe being supposed to have been a secret of the Papal kitchens in Rome), and served especially to cleanse the palate between courses.

Origin

Early 19th century; earliest use found in Thomas Moore (1779–1852), poet. Probably after French punch romain and (in later use) punch à la romaine.