Spur
horse's rider, such as a jockey or cowboy, to goad the horse into running faster.
Spurs are also used by dressage riders. In this case they are used not to speed up a horse, but to give him accurate and precise aids in lateral movements or more complicated movements, such as airs above the ground.
Spurs used by dressage rides tend to be blunt and shaped so as to give a signal but not cause pain for a horse.
A plain or spiked (usually in western riding style) wheel is called a rowel.
Derivative meanings
A number of other things are called "spur" by the analogy with the main meaning of the word.
