Synonyms and related words :
agile, breakneck, dashing, double-quick, eagle-winged, expeditious, express, fast, fleet, flying, galloping, hair-trigger, hasty, headlong, hustling, light of heel, light-footed, lively, mercurial, nimble, nimble-footed, precipitate, prompt, quick, quick as lightning, quick as thought, rapid, reckless, running, snappy, spanking, speedy, swift