Definition of high-mettled in US English:

high-mettled

adjective

archaic
  • Having or characterized by considerable courage or spirit; (especially of a horse) lively, headstrong.

Origin

Early 17th century; earliest use found in Francis Bacon (1561–1626), lord chancellor, politician, and philosopher. From high + mettled.

Pronunciation

high-mettled

/ˌhʌɪˈmɛtld/