Slow in motion

sluggish, laggard, deliberate, gradual, moderate, loitering, leaden, creeping, inactive, torpid, slow moving, ultra-slow, crawling, imperceptible, snaillike, slow-paced, leisurely, glue-footed*, as slow as molasses*, as slow as molasses in January*.

Antonyms fast*, swift*, rapid. *

Slow in starting

dilatory, procrastinating, delaying, postponing, idle, indolent, tardy, torpid, lazy, apathetic, phlegmatic, inactive, fabian, sluggish, heavy, quiet, drowsy, inert, dreamy, sleepy, lethargic, stagnant, slothful, supine, passive, slack, negligent, remiss, listless, languorous, lackadaisical, disinclined, reluctant, hesitant, enervated, dormant, abeyant, potential, latent; see also late 1.

Antonyms immediate*, alert*, instant. *

Slow in producing an effect

belated, behindhand, backward, unpunctual, overdue, delayed, long-delayed, behindtime, regarded, impeded, detained, hindered, moss-backed.

Antonyms busy*, diligent*, industrious. *

Dull or stupid

stolid, tame, uninteresting; see dull 3. See syn. study at stupid.

To become slower

slacken, slow up, slow down, lag, loiter, quiet, relax, procrastinate, back water, back and fill, stall*, let up*, wind down*, ease up*, ease off*; see also sense 2, decrease 1, hesitate.

Antonyms rise*, accelerate*, mount. *

To cause to become slower

delay, postpone, decelerate, moderate, reduce, regulate, retard, detain, temper, qualify, decrease, diminish, hinder, impede, hold back, keep waiting, brake, curtail, check, curb, reef, shorten sail, cut down*, rein in*, cut back*; see also sense 1.