Definition of Matthew's pill in US English:

Matthew's pill

(also Mathew's pill)

noun

historical
  • A pill sold as an antidote to various poisons.

Origin

Mid 17th century; earliest use found in Newes. From the genitive of the name of Richard Mathew (died 1661), English medical practitioner, who manufactured and sold the pill + pill.

Pronunciation

Matthew's pill

/ˈmaθjuːz ˌpɪl/