Mask:  In hunting, the face of the fox.

Master of Fox Hounds:  The man (or woman) who has charge of both the season's sport and the social aspects of the hunt.  (Some 121 hunts are currently {1974} active, according to the Masters of Fox Hounds Association of America.)  The M.F.H. is a person respected for his hunting skill and his diplomacy in dealing with field members, professional huntsmen, and property owners.  He is responsible for maintaining a good pack of hounds and for planning and presiding over successful days afield.  On a hunt the M.F.H. may also act as huntsman or field master.

Mealy nose or muzzle:  Unpigmented, flesh- or dun-coloured muzzle.

Mesomorphic:  A group of classification in which may be found most riding horses and light workhorses, such as the Arabian.

Meso-brachymorphic:  A type of horse that combines mesomorphic and brachymorphic traits, like the Friesian.

Meso-dolichomorphic:  A type of horse that combines mesomorphic and dolichomorphic traits, such as the Trakehner and other European Warmbloods.

Mob:  In hunting, the action of the pack in killing the fox before it has a chance to run.

Morgan:  A small strong American breed of horse descended from Justin Morgan's famous little bay stallion of the late 1700s.

Mucking out:  Cleaning a stall.