horse

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A large hoofed mammal (Equus caballus) having a short coat, a long mane, and a long tail, domesticated since ancient times and used for riding and for drawing or carrying loads.
• noun An adult male horse; a stallion.
• noun Any of various equine mammals, such as the wild Asian species Przewalski's horse or certain extinct forms related ancestrally to the modern horse.
• noun A frame or device, usually with four legs, used for supporting or holding.
• noun Sports A vaulting horse.
• noun Slang Heroin.
• noun Horsepower.
• noun Mounted soldiers; cavalry.
• noun A block of rock interrupting a vein and containing no minerals.
• noun A large block of displaced rock that is caught along a fault.
• intransitive verb To provide with a horse.
• intransitive verb To haul or hoist energetically.
• intransitive verb To be in heat. Used of a mare.
• adjective Of or relating to a horse.
• adjective Mounted on horses.
• adjective Drawn or operated by a horse.
• adjective Larger or cruder than others in the same category.
• idiom (a horse of another/a different) Another matter entirely; something else.
• idiom (beat/flog) To continue to pursue a cause that has no hope of success.
• idiom (beat/flog) To dwell tiresomely on a matter that has already been decided.
• idiom (be/get) To be or become disdainful, superior, or conceited.
• idiom (hold (one's) horses) To restrain oneself.
• idiom (the horse's mouth) A source of information regarded as original or unimpeachable.

from The Century Dictionary.

• To provide with a horse; supply horses for, as a body of cavalry, etc.
• To sit astride; bestride.
• To cover: said of the male.
• To mount or place on or as on the back of a horse; set on horseback; hence, to take on one's own back.
• To mount on another's back preparatory to flogging.
• . Nautical, to “ride” hard; drive or urge at work unfairly or tyrannically: as, to horse a ship's crew.
• To make out or learn by means of a translation or other extrinsic aid: as, to horse a lesson in Virgil.
• To get on horseback; mount or ride on a horse.
• To charge for work before it is executed.
• In calking, to embed firmly in the seams of a ship, as oakum, with a horsing-iron and a mallet: often with up.
• To hang (as skins) over a wooden horse or stand.
• noun The researches of Ewart, Osborn, and others show the probability that the modern horse, like the dog, has been derived from several sources. Prjevalsky's horse is considered to be one of these, while two other forms are recognized—the Celtic pony and the Norse horse.
• noun One of the inclined timbers in a staircase which support the steps.
• noun In mining: A lenticular bod of shale or old channel fillings which cuts out coal-seams.
• noun In chess, same as knight.
• noun In astronomy, the constellation of Pegasus (see flying horse); also, the equine part of Sagittarius (represented as a centaur).
• noun A Danish silver coin of the value of 1 s. 2 d.
• An obsolete form of hoarse.
• noun A solidungulate perissodactyl mammal of the family Equidœ and genus Equus; E. caballus.
• noun plural In zoology, the horse family, or Equidæ; the species of the genus Equus and related genera.
• noun The male of the horse kind, in distinction from the female or mare; a stallion or gelding.
• noun A body of troops serving on horseback: cavalry: in this sense a collective noun, used also as a plural: as, a regiment of horse.
• noun A frame, block, board, or the like, on which something is mounted or supported, or the use of which is in any way analogous to that of a horse. Compare etymology of easel.
• noun Specifically— A vaulting-block in a gymnasium.