Synonyms and related words :
active, acute, adroit, agile, alacritous, alert, alive, apt, attentive, awake, brainy, breakneck, bright, brilliant, brisk, catty, clever, coruscating, dashing, deft, dexterous, dispatchful, double-quick, eagle-winged, energetic, expeditious, express, fast, featly, fleet, flying, galloping, gifted, graceful, hair-trigger, handy, hasty, headlong, hustling, intelligent, keen, keen-witted, light, light of heel, light-footed, lightsome, limber, lithe, lively, mercurial, neat-fingered, neat-handed, nimble-footed, nimble-witted, no dumbbell, not born yesterday, on the, on the alert, on the ball, on the job, peart, precipitate, prompt, qui vive, quick, quick as lightning, quick as thought, quick-thinking, quick-witted, rapid, ready, reckless, running, scintillating, sharp, sharp-witted, sleepless, smart, snappy, spanking, sparkling, speedy, sprightly, spry, steel-trap, sure-footed, swift, talented, unblinking, unnodding, unsleeping, unwinking, vigilant, wakeful, watchful, wide-awake, winged, zippy