What is "cruppers"

Usage examples of "cruppers".

There were bright pin-up calendars, promising, after the mild though windy winter, torrid abandon renewed, golden flesh, the heartbreaking wagging cruppers of the bikinied young over the golden beaches.

And they gave each other such a shock, that the girths of their horses were broken, so that they fell over their horses' cruppers to the ground.

A confusion of helmets, of cries, of sabres, a stormy heaving of the cruppers of horses amid the cannons and the flourish of trumpets, a terrible and disciplined tumult.