What is one who rides and guides the first pair of horses of a coach or post chaise; also, one who rides one of the horses when one pair only is used. [Written also postillion.] called?

postilion — One who rides and guides the first pair of horses of a coach or post chaise; also, one who rides one of the horses when one pair only is used. [Written also postillion.]. (Webster's 1913.)

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