Synonyms of fast

1 Syllable

lewd, stuck, staunch, quick, brisk, snap, diet, flying, hot, swift, soon, fleet, tight, pdq

2 Syllables

nighthawk, wedged, proofer, breakneck, flashing, stably, dizzying, soonest, clubby, hasty, fleetest, lewdest, dieting, dieted, hastier, sit-in, tightest, abstain, steadfast, tighter, sit-down, love-in, clubbier, racing, instant, dashing, speeder, fleetly, fleeter, deeping, stauncher, starve, lowdown, hastiest, skintight, ribald, jammed, staunchest, fixed, lieger, sudden, firmly, nimble, speedball, wantons, clingy, ready, promptly, soft-core, low-down, wanton, presto, stablest, snappy, faithful, fleeting, brick-wall, sooner, stabler, rapid, abstains, hurried, chop-chop, pronto, half-assed, raffish, rakish, winged

3 Syllables

on-the-spot, durable, split-second, fence-sit, durably, abstained, agile, licentious, rapider, debauched, electric, foul-mouthed, unvirtuous, hair-trigger, salacious, subito, diuturnal, stabile, hastily, posthaste, alate, lubricous, dietaries, depraved, pennate, promiscuous, snappily, cursory, abstaining, tenacious, punctually, padlocked, barreling, active, lickerish, immoral, satyric, unmoral, lascivious, speedily, orgiastic, amoral, rapidly, softcore, unbroken, abiding, speeded-up, double-time, hairtrigger, screamin', velocious, lecherous

4 Syllables

supersonic, hypersonic, instantaneous, unshakeably, libidinous, dissolute, undivided, immovable, buddy-buddy, undistracted, long-continued, malfunctioning, intensive, intimate, close-fitting, unforgetful, never-failing, unmovable, expeditious, nimble-footed, ungoverned, lickety-split, oversexed, unconstrained

5 Syllables

expeditiously, expeditive, accelerated

6 Syllables

precipitately

7 Syllables

unpremeditatedly