horse 
(hôrs)
(hôrs)n.
1.
a. 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.
b. An adult male horse; a stallion.
c. Any of various equine mammals, such as the wild Asian species Przewalski's horse or certain extinct forms related ancestrally to the modern horse.
2. A frame or device, usually with four legs, used for supporting or holding.
3. Sports A vaulting horse.
4. Slang Heroin.
5. often horses Horsepower: a muscle car with 400 horses under the hood.
6. Mounted soldiers; cavalry: a squadron of horse.
7. Geology
a. A block of rock interrupting a vein and containing no minerals.
b. A large block of displaced rock that is caught along a fault.
v. horsed, hors·ing, hors·es
v.tr.
1. To provide with a horse.
2. To haul or hoist energetically: "Things had changed little since the days of the pyramids, with building materials being horsed into place by muscle power" (Henry Allen).
v.intr.
To be in heat. Used of a mare.
adj.
Phrasal Verb: 1. Of or relating to a horse: a horse blanket.
2. Mounted on horses: horse guards.
3. Drawn or operated by a horse.
4. Larger or cruder than others in the same category: horse pills.
horse around Informal
Idioms: To indulge in horseplay or frivolous activity: Stop horsing around and get to work.
a horse of another/a different color
Another matter entirely; something else.
beat/flog a dead horse
1. To continue to pursue a cause that has no hope of success.
2. To dwell tiresomely on a matter that has already been decided.
be/get on (one's) high horse
To be or become disdainful, superior, or conceited.
hold (one's) horses
To restrain oneself.
the horse's mouth
A source of information regarded as original or unimpeachable.
[Middle English, from Old English hors; akin to Old Norse hross, horse, and German Ross, steed.]