Source : Webster's Revised Unabridged Dictionary (1913)

Massiveness \Mass"ive*ness\, n.
   The state or quality of being massive; massiness.

Source : WordNet®

massiveness
     n 1: an unwieldy largeness [syn: {bulkiness}]
     2: the property of being large in mass [syn: {heft}, {heftiness},
         {ponderousness}, {ponderosity}]