adjective
very fast
Synonyms: abrupt, alacritous, barrelling, breakneck, cracking, double-quick, expeditious, express, fleet, fleet-footed, flying, hasty, headlong, hurried, in nothing flat, like crazy, like mad, nimble, on the double, precipitate, prompt, pronto, quick, rapid, ready, screaming, shaking a leg, short, short-lived, snappy, spanking, speedball, speedy, sudden, supersonic, unexpected, winged
Antonyms: delayed, slow, sluggish
adverb
very fast
Synonyms: apace, double-quick, expeditiously, flat-out, fleetly, full tilt, hastily, hurriedly, in no time, posthaste, promptly, quick, quickly, rapidly, speedily, without losing time, without warning
Antonyms: slowly, sluggishly