The Collaborative International Dictionary of English v.0.48:

Slothful \Sloth"ful\, a.
   Addicted to sloth; inactive; sluggish; lazy; indolent; idle.
   [1913 Webster]

         He also that is slothful in his work is brother to him
         that is a great waster.                  --Prov. xviii.
                                                  9.
   [1913 Webster] -- Sloth"ful*ly, adv. -- Sloth"ful*ness,
   n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

slothful
    adj 1: disinclined to work or exertion; "faineant kings under
           whose rule the country languished"; "an indolent hanger-
           on"; "too lazy to wash the dishes"; "shiftless idle
           youth"; "slothful employees"; "the unemployed are not
           necessarily work-shy" [syn: faineant, indolent,
           lazy, otiose, slothful, work-shy]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "slothful":
   ambling, apathetic, bone-lazy, cadging, cautious, circumspect,
   claudicant, crawling, creeping, creeping like snail, deliberate,
   dilatory, do-nothing, doless, dronish, drony, easy, easygoing,
   ergophobic, faineant, faltering, flagging, foot-dragging, gentle,
   good-for-nothing, gradual, halting, hebetudinous, hobbled,
   hobbling, idle, inactive, indifferent, indolent, inert,
   lackadaisical, laggard, languid, languorous, lax, lazy, leisurely,
   lethargic, limping, lumbering, moderate, nonaggressive, parasitic,
   phlegmatic, pococurante, poking, poky, procrastinative, relaxed,
   reluctant, remiss, sauntering, scrounging, shiftless, shuffling,
   slack, slow, slow as death, slow as molasses, slow as slow,
   slow-crawling, slow-foot, slow-going, slow-legged, slow-moving,
   slow-paced, slow-poky, slow-running, slow-sailing, slow-stepped,
   sluggish, snail-paced, snaillike, sponging, staggering, strolling,
   tentative, toddling, torpid, tortoiselike, tottering, trudging,
   turtlelike, unenterprising, unhurried, waddling, work-shy