A garron or garran is a type of horse. The term occurs in Scotland and in Ireland, and generally refers to an undersized and much-despised beast.
In Scotland a Garron is one of the types of Highland pony. It is the larger, heavier type bred on the mainland. The isles' type of Highland pony is generally smaller and lightly finer, but still within the bred standard. There is less difference today than there once was between these two types.
The phrase Garron was also use to describe a highland cross of a Clydesdale horse used in farming, especially in the highlands and isles where a full size Clydesdale would not have been as economical.
Also, see garrano, an ancient Portuguese breed of pony.
In "MacBeth The King" by Nigel Tranter, a garron is one of the larger war horses used by knights wearing heavy armor, as opposed to a "birlinn" -- a smaller, finer boned, faster horse, usually of Arabian descent. The word garron is also mentioned a number of times in George R.R. Martin's novels in "A Song of Ice and Fire", the fantasy series which began with "A Game of Thrones". There the context inferred that it was a small, hardy breed of pony suitable for use in cold, mountainous areas, generally to the North near The Wall.