The Collaborative International Dictionary of English v.0.48:

Lamentable \Lam"en*ta*ble\, a. [L. lamentabilis: cf. F.
   lamentable.]
   1. Mourning; sorrowful; expressing grief; as, a lamentable
      countenance. [Archaic] "Lamentable eye." --Spenser.
      [1913 Webster]

   2. Fitted to awaken lament; to be lamented; sorrowful;
      pitiable; regrettable; unfortunate; as, a lamentable
      misfortune, or error. "Lamentable helplessness." --Burke.
      [1913 Webster]

   3. Miserable; pitiful; paltry; -- in a contemptuous or
      ridiculous sense. --Bp. Stillingfleet. --
      Lam"en*ta*ble*ness, n. -- Lam"en*ta*bly, adv.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lamentable
    adj 1: bad; unfortunate; "my finances were in a deplorable
           state"; "a lamentable decision"; "her clothes were in sad
           shape"; "a sorry state of affairs" [syn: deplorable,
           distressing, lamentable, pitiful, sad, sorry]

Moby Thesaurus II by Grady Ward, 1.0:

120 Moby Thesaurus words for "lamentable":
   abominable, affecting, afflictive, aggrieved, anguished, arrant,
   atrocious, awful, base, beastly, beneath contempt, bitter,
   blameworthy, bleak, brutal, calamitous, careworn, cheerless,
   comfortless, contemptible, deplorable, depressing, depressive,
   despicable, detestable, dire, discomforting, disgusting, dismal,
   dismaying, distressful, distressing, doleful, dolorific,
   dolorogenic, dolorous, dreadful, dreary, dumb with grief,
   egregious, enormous, fetid, filthy, flagrant, foul, fulsome,
   grief-stricken, griefful, grieved, grievous, gross, hateful,
   heartbreaking, heinous, horrible, horrid, in grief, infamous,
   intolerable, joyless, loathsome, lousy, lugubrious, miserable,
   monstrous, mournful, moving, nasty, nefarious, noisome, notorious,
   obnoxious, odious, offensive, outrageous, painful, pathetic,
   piteous, pitiable, pitiful, plaintive, plangent, plunged in grief,
   poignant, rank, regrettable, reprehensible, repulsive, rotten,
   rueful, sad, saddening, scandalous, schlock, scurvy, shabby,
   shameful, sharp, shocking, shoddy, sordid, sore, sorrowed,
   sorrowful, sorrowing, squalid, tearful, terrible, too bad,
   touching, unclean, uncomfortable, unfortunate, vile, villainous,
   woebegone, woeful, worst, worthless, wretched