M

Maiden
A class/division open to a rider (or horse) who
has not won a blue ribbon at specified shows.

Maiden mare
Mare that has never been bred (also barren).

Mammoth Mule
The result of breeding mammoth donkeys to horse mares.
Mammoth Mules.com

Manners
How a horse behaves around other horses and humans.
The level of training a horse has had that helps him with his interaction with humans.

Mare
A female horse over age four.

Mark
A score you earn/accumulate.

Marker
In reining, a location for a pattern.

Markings
White on the face and legs of the horse. Body markings in white are considered pinto markings.

Martingale
Training equipment that works on the horse's head. German, standing, running.
April Reeves Video: The German Martingale: Use and Function

Maturities
Events/classes for horses five and older.

Mecate
Braided horsehair reins usually found on a bosal.

Meconium
Fecal matter that a foal passes a few hours
after birth.

Medal Class
AHSA equitation competition. National
champions are chosen annually at Harrisburg, Pennsylvania, in hunter seat,
saddle seat, and stock seat and a dressage class for juniors.

Medium Gait
A gait in between collected and extended. Sometimes referred to as 'working'.

Moon blindness
Inability to see in dim light, from a retinal disorder or lack of vitamin A.

Mule
The cross between a female horse to a male donkey. The result is an extremely hardy, athletic and versatile partner.
Mules (general article)
Mules, Wikipedia

Mule, Mini
The cross between a miniature horse mare and a miniature donkey male.
Miniature Mule Society

Muzzle
The end of a horse's face (nose, nostrils, and lips).