Small spiked wheels on the ends of spurs that are used to make a horse move faster.
Rowels are usually used by people who ride horses, like cowboys.
Examples:
The cowboy's boots had rowels on the spurs.
The rowels on the spurs jingled as the cowboy rode.
The rowels spun as the cowboy kicked the horse.
The rowels on the spurs made the horse go really fast!
The rowels on the spurs looked sharp and shiny.
The cowboy's rowels were as big as coins.