Very clever, highly intelligent. The sharp crack of a whip has been a metaphor for mental quickness since the mid-nineteenth century in America. “He was as smart as a whip,” wrote B. F. Taylor (World on Wheels, 1874), one of the early appearances of this expression in print. Several writers, among them Harriet Beecher Stowe and Erle Stanley Gardner, have used smart as a steel trap, presumably alluding to its rapidly closing on some hapless creature, but it has not replaced the older simile.