The Collaborative International Dictionary of English v.0.48:

cumbersome \cum"ber*some\ (k?m"b?r-s?m), a.
   1. Burdensome or hindering, as a weight or drag;
      embarrassing; vexatious; cumbrous.
      [1913 Webster]

            To perform a cumbersome obedience.    --Sir. P.
                                                  Sidney.
      [1913 Webster]

   2. Not easily managed; as, a cumbersome contrivance or
      machine.
      [1913 Webster]

            He holds them in utter contempt, as lumbering,
            cumbersome, circuitous.               --I. Taylor.
      -- Cum"ber*some*ly, adv. -- Cum"ber*some*ness,n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cumbersome
    adj 1: difficult to handle or use especially because of size or
           weight; "a cumbersome piece of machinery"; "cumbrous
           protective clothing" [syn: cumbersome, cumbrous]
    2: not elegant or graceful in expression; "an awkward prose
       style"; "a clumsy apology"; "his cumbersome writing style";
       "if the rumor is true, can anything be more inept than to
       repeat it now?" [syn: awkward, clumsy, cumbersome,
       inapt, inept, ill-chosen]

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "cumbersome":
   all thumbs, awkward, blunderheaded, blundering, boorish, bulky,
   bumbling, bungling, burdensome, butterfingered, careless, clownish,
   clumsy, clumsy-fisted, contrary, crosswise, cumbrous, elephantine,
   encumbering, fingers all thumbs, fumbling, gauche, gawkish, gawky,
   graceless, ham-fisted, ham-handed, hampering, heavy-handed,
   hulking, hulky, impedimental, impeding, impeditive, impractical,
   inconvenient, incumbent, inelegant, irksome, left-hand,
   left-handed, loutish, lubberly, lumbering, lumpish, lumpy,
   maladroit, massive, massy, oafish, onerous, oppressive, perverse,
   ponderous, sloppy, stiff, superincumbent, tiresome, uncouth,
   ungainly, ungraceful, unhandy, unmanageable, unwieldy, wearisome