Warmblood: In general terms, a half-bred, or part-bred horse, the result of an Arabian or Thoroughbred cross with other breeds. Also one of a number of specific breeds of horse which were developed by crossing hotblood and coldblood horses to produce a more refined, but athletically strong and capable horse, such as the Swedish Warmblood, the Dutch Warmblood etc.
Weedy: A horse of poor conformation, generally weak in the quarters and shoulders, with long legs.
Weight carrier: Another term for heavyweight, i.e. a horse capable of carrying 210 lb.
Well Ribbed-Up: A short, deep, well-rounded body with well-sprung ribs.
Well-Sprung Ribs: Long rounded ribs giving ample room for lung expansion, well suited to carrying a saddle.
Wheeler: The horse harnessed closest to the carriage, behind the leader.
Whip: The driver of a carriage.
Whipper-In: The assistant to the huntsman of a pack of hounds.
Wind Sucking: Stable vice in which the horse arches his neck and sucks air in through his open mouth. When the horse latches his teeth on to a solid surface in order to suck air, he is called a cribber, or a crib biter.
Withers: Point at the bottom of the horse's neck from which the horse's height is measured.