postillion vs equestrian

postillion and equestrian both are nouns.

Word	Noun	Adjective	Verb	Adverb
postillion	Yes	No	No	No
equestrian	Yes	Yes	No	No

As nouns, equestrian is a hypernym of postillion; that is, equestrian is a word with a broader meaning than postillion:

postillion: someone who rides the near horse of a pair in order to guide the horses pulling a carriage (especially a carriage without a coachman)
equestrian: a person skilled in equitation

Other hypernyms of postillion include horseback rider.

postillion (noun)	equestrian (noun)
someone who rides the near horse of a pair in order to guide the horses pulling a carriage (especially a carriage without a coachman)	a person skilled in equitation

postillion (adjective)	equestrian (adjective)
	of or relating to or featuring horseback riding
	of or relating to or composed of knights