Same word as smart:

acute, adept, agile, alert, apt, astute, bold, brainy, bright, brilliant, brisk, canny, clever, crafty, effective, eggheaded, fresh, genius, good, impertinent, ingenious, keen, knowing, long-haired, nervy, nimble, on the ball, pert, pointed, quick, quick-witted, ready, resourceful, sassy, sharp, shrewd, skull, slick, whiz, wise