The Collaborative International Dictionary of English v.0.48:

Worthless \Worth"less\, a. [AS. weor[eth]le['a]s.]
   Destitute of worth; having no value, virtue, excellence,
   dignity, or the like; undeserving; valueless; useless; vile;
   mean; as, a worthless garment; a worthless ship; a worthless
   man or woman; a worthless magistrate.
   [1913 Webster]

         'T is a worthless world to win or lose.  --Byron.
   [1913 Webster] -- Worth"less*ly, adv. -- Worth"less*ness,
   n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

worthless
    adj 1: lacking in usefulness or value; "a worthless idler" [ant:
           valuable]
    2: morally reprehensible; "would do something as despicable as
       murder"; "ugly crimes"; "the vile development of slavery
       appalled them"; "a slimy little liar" [syn: despicable,
       ugly, vile, slimy, unworthy, worthless, wretched]

Moby Thesaurus II by Grady Ward, 1.0:

140 Moby Thesaurus words for "worthless":
   NG, abominable, arrant, atrocious, awful, base, beastly, beggarly,
   beneath contempt, beneath notice, blameworthy, bootless, brutal,
   cheap, cheesy, common, contemptible, crummy, defective,
   deleterious, deplorable, despicable, detestable, detrimental, dire,
   disadvantageous, disgusting, disserviceable, dreadful, dusty,
   egregious, enormous, fetid, filthy, flagrant, flawed, foul,
   fulsome, fustian, gaudy, gimcracky, good-for-naught,
   good-for-nothing, grievous, gross, harmful, hateful, heinous,
   horrible, horrid, imperfect, incapable, incompetent, ineffectual,
   infamous, inferior, injurious, junk, junky, lamentable, loathsome,
   lousy, mean, meaningless, mediocre, meretricious, meritless,
   miserable, monstrous, nasty, nefarious, no-account, no-good,
   noisome, not worth having, not worth mentioning, not worthwhile,
   nothing, notorious, nugacious, nugatory, obnoxious, odious,
   offensive, outrageous, paltry, pathetic, pitiable, pitiful, poor,
   prejudicial, purposeless, rank, regrettable, reprehensible,
   repulsive, rotten, rubbishy, sad, scandalous, schlock, scrubby,
   scruffy, scummy, scurvy, scuzzy, second-rate, shabby, shameful,
   shocking, shoddy, sordid, sorry, squalid, terrible, too bad,
   trashy, trivial, trumpery, two-for-a-cent, two-for-a-penny,
   twopenny, twopenny-halfpenny, unadvantageous, unavailing, unclean,
   unfavorable, unprofitable, unpurposed, unqualified, unrewarding,
   unworthy, unworthy of regard, useless, valueless, vile, villainous,
   woeful, worst, wretched