Definition of post-horse in US English:

post-horse

noun

historical
  • A horse kept at a post-house or inn for the use of post-riders, or for hire by travellers.

Origin

Early 16th century; earliest use found in Stephen Gardiner (d. 1555), theologian, administrator, and bishop of Winchester. From post + horse.

Pronunciation

post-horse

/ˈpəʊsthɔːs/