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):

cumbersomeness
    n 1: trouble in carrying or managing caused by bulk or shape;
         "the movers cursed the unwieldiness of the big piano" [syn:
         awkwardness, cumbersomeness, unwieldiness]