Definition of Mason–Dixon line in US English:

Mason–Dixon line

noun

  • (in the US) the boundary between Maryland and Pennsylvania, taken as the northern limit of the slave-owning states before the abolition of slavery.

Origin

Named after Charles Mason and Jeremiah Dixon, the 18th-century English astronomers who surveyed it in 1763–7.

Pronunciation

Mason–Dixon line

/ˌmāsənˈdiksən ˌlīn//ˌmeɪsənˈdɪksən ˌlaɪn/