The doorpost of a victualer's shop or inn, on which were chalked the scores of customers; hence, a score; a debt.
Haste or speed, like that of a messenger or mail carrier.
To travel with post horses; figuratively, to travel in haste.
To rise and sink in the saddle, in accordance with the motion of the horse, esp. in trotting.
With post horses; hence, in haste; as, to travel post.
To rise from the saddle in rhythm with the horse's trot.
ride Western style and bob up and down in the saddle in in rhythm with a horse's trotting gait