Anything that's speedy moves with rapid speed, whether it's a bullet train or a waiter bringing coffee before you’ve even finished ordering it. If your brother sends you on an errand, he might call, "Be speedy!" especially if you're known for taking your time. The Old English root of speedy is spedig, which curiously means "wealthy." A now old fashioned meaning of "speed," in fact, was "success" or "prosperity.”