post horse(n = noun.animal) post-horse, poster - a horse kept at an inn or post house for use by mail carriers or for rent to travelers;
is a kind of equus caballus, horse

N  carrier, porter, bearer, tranter, conveyer, cargador, express, expressman, stevedore, coolie, conductor, locomotive, motor, beast, beast of burden, cattle, horse, nag, palfrey, Arab, blood horse, thoroughbred, galloway, charger, courser, racer, hunter, jument, pony, filly, colt, foal, barb, roan, jade, hack, bidet, pad, cob, tit, punch, roadster, goer, racehorse, pack horse, draft horse, cart horse, dray horse, post horse, ketch, Shetland pony, shelty, sheltie, garran, garron, jennet, genet, bayard, mare, stallion, gelding, bronco, broncho, cayuse, creature, critter, cow pony, mustang, Narraganset, waler, stud, Pegasus, Bucephalus, Rocinante, ass, donkey, jackass, mule, hinny, sumpter horse, sumpter mule, burro, cuddy, ladino, reindeer, camel, dromedary, llama, elephant, carrier pigeon, pallet, brace, cart, dolley, support, fork lift, carriage, ship, equine, asinine.

american saddle horse, binding post, c. w. post, cart horse, cavalry horse, charles william post, charley horse, coach horse, command post, corner post, cossack post, crazy horse, dark horse, dawn horse, deaf as a post, draft horse, draught horse, dray horse, emily post, emily price post, ex post facto, farm horse, female horse, from pillar to post, gift horse, goal post, gymnastic horse, harness horse, high horse, hinging post, hitching post, horse, horse around, horse balm, horse barn, horse bean, horse blanket, horse botfly, horse breeding, horse brier, horse cart, horse cassia, horse cavalry, horse chestnut, horse doctor, horse fancier, horse fly, horse gentian, horse grain, horse gram, horse guards, horse latitude, horse latitudes, horse mackerel, horse manure, horse mushroom, horse nettle, horse of the wood, horse opera, horse parsley, horse pistol, horse power, horse race, horse racing, horse radish, horse sense, horse show, horse thistle, horse tick, horse trade, horse trader, horse trading, horse wrangler, iron horse, king post, local post office, long horse, male horse, meteorological observation post, military post, missionary post, newel post, observation post, one horse, pack horse, parcel post, plantation walking horse, plough horse, plow horse, pole horse, pommel horse, post, post and lintel, post card, post chaise, post doc, post exchange, post hoc, post hoc ergo propter hoc, post hole, post horn, post house, post meridiem, post note, post oak, post office, post road, przevalski's horse, przewalski's horse, quarter horse, queen post, race horse, registered post, riding horse, river horse, rocking horse, saddle horse, sea horse, shire horse, shutting post, side horse, stalking horse, starting post, stick horse, swinging post, telegraph post, tennessee walking horse, three-year-old horse, totem post, towel horse, trading post, trojan horse, trotting horse, two-year-old horse, united states post office, us post office, vaulting horse, walking horse, war horse, wheel horse, whipping post, white horse, white horse nettle, wild horse, wiley post, winning post, wooden horse