Synonyms for Slow:

adj.

behind, late (adjective)
belated, delayed, down, dull, lingering, off, overdue, prolonged, tame, tedious.
dim (adjective)
Weak-minded.
dull (adjective)
apathetic, benumbed, besotted, blunt, boorish, bovine, cloddish, comatose, dense, dim, doltish, drowsy, dull, lethargic, loutish, obtuse, ponderous, sleepy, sluggish, soporific, stupefied, thick-witted.
gradual (adjective)
gradual.
late (adjective)
belated, tardy.
leisurely (adjective)
unhurried.
lethargic (adjective)
dopey, drooping, drugged, indolent, insensible, lackadaisical, languid, languorous, lazy, leaden, leisurely, lifeless, listless, lumpish, phlegmatic, slothful, tired, torpid, unhurried, apathetic, benumbed, dull, lethargic, sluggish.
oafish (adjective)
lumpish.
procrastinating (adjective)
dilatory.
slow (adjective)
crawling, creeping, dawdling, dragging, lingering, plodding, poky, slowpoke, Delaying, Loitering, Trudging, leisurely, lethargic, phlegmatic, sluggish.
thick (adjective)
slow-witted.
unhurried, lazy (adjective)
apathetic, crawling, creeping, dawdling, deliberate, dilatory, dreamy, drowsy, easy, gradual, idle, imperceptible, inactive, indolent, lackadaisical, laggard, leaden, leisurely, lethargic, listless, measured, moderate, negligent, passive, phlegmatic, plodding, ponderous, quiet, remiss, slack, sleepy, slothful, slow-moving, sluggish, stagnant, supine, tardy, torpid, Delaying, Loitering.
unintelligent (adjective)
dense, dim, dumb, obtuse, simple.

adv.

all (adverb)
behind, easy, slowly, tardily.

n.

about, after, ahead, around, at, deliberate, fast, forward, gradual, half-hour, imperceptible, moderate, swift, AM, slow-paced. abeyant, acoustic, alert, atonal, bass, classical, discordant, dormant, dreamy, funky, harmonic, harmonious, hesitant, idle, immediate, latent, negligent, passive, potential, quiet, remiss, stagnant, supine, tardy, bluesy. belated, busy, constant, delayed, diligent, enduring, extended, lasting, long, long-term, never-ending, overdue, prolonged, on and on, for some time. stolid, tame, trivial, unexciting, uninspired. aperture, boom, camcorder, camera, cartridge, celluloid, darkroom, developer, Asa, slow-footed, slow-going, digicam. arterial, down, feeder, impassable, increase, off, one-way, passable, sharp, tight, two-way. ability, half-witted, idiotic, silly, simple, simple-minded, slow-witted, Feeble-minded, Weak-minded. cut back, decrease, erode, halve, lower, minimize, reduce, shrivel, time, trim down, top-slice, behind time. barbecue, beater, blender, broiler, burner, coffee maker, colander, cooker, Barbie, coffee machine. brake, ease off, grind to a halt, throttle back. measured, sedate, stately, steady. slow (noun)
adagio, andante, behind, boring, bumper-to-bumper, crawling, dawdling, deadening, decelerate, dense, dilatory, dim, dragging, drawling, drawn-out, dull, dumb, easy, ho-hum, inactive, laggard, larghetto, larghissimo, largo, lazy, lentissimo, lento, long-play, long-playing, moderato, obtuse, pokey, poky, slack, slacken, slow down, slow up, slow-moving, slowly, sluggish, tardily, tedious, tiresome, uninteresting, wearisome, Irksome.

v.

delay, restrict (verb)
brake, cut back, decelerate, decrease, ease off, hinder, loiter, reduce, slacken.
slow (verb)
crawl, creep, dawdle, delay, drag, hesitant, hinder, linger, loiter, plod, poke, trudge.

Other synonyms:

dormant, idiotic, impassable, latent, measured, slow-witted, stagnant, slow-footed, slow-going, slow-paced, throttle back. arterial, ease off, half-witted, sedate, simple-minded, stately, Feeble-minded. brake, deliberate, feeder, one-way, silly, two-way, Weak-minded. down, simple. off, steady, tight. decrease
slacken.
irksome
Irksome.
moderate
ease off.
slow down
decelerate.
Other relevant words:
behind, belated, deliberate, ease off, easy, gradual, inactive, laggard, moderate, overdue, pokey, slack, slacken, slow down, slow up, slow-witted, slowly, stolid, tardy, behind time.

Usage examples for slow

  1. He got up, and even made one slow step towards the door; but he did not go out, nor did he seem afraid of me. – A Witch of the Hills, v. 1-2 by Florence Warden
  2. But he'll be slow to part wi' other things, too. – Between You and Me by Sir Harry Lauder
  3. You'll find it rather- rather slow at the school, won't you? – The Varmint by Owen Johnson F. R. Gruger