Mane and Forelock

Long and relatively coarse hair growing from the dorsal ridge of the neck, lying on either the left or right side of the neck, and the continuation of that hair on the top of the head, where it generally hangs forward.

Mare

A female horse usually over 4 years old.

Martingale

A piece of harness used on a horse to keep it from raising its head above a desired point

Milkshakes

A combination of bicarbonate of soda mixed with a liquid that is believed to reduce fatigue and therefore enhance performance in horses.

Mule

Sterile hybrid offspring of a male donkey and a female horse.

Muzzle

The chin, mouth, and nostrils make up the muzzle on the horse's face.