Source : Webster's Revised Unabridged Dictionary (1913)

Ponderosity \Pon`der*os"i*ty\, n.; pl. {Ponderosities}. [OF.
   ponderosit['e].]
   The quality or state of being ponderous; weight; gravity;
   heaviness, ponderousness; as, the ponderosity of gold. --Ray.

Source : WordNet®

ponderosity
     n : the property of being large in mass [syn: {heft}, {heftiness},
          {massiveness}, {ponderousness}]