Source : Webster's Revised Unabridged Dictionary (1913)

Weightiness \Weight"i*ness\, n.
   The quality or state of being weighty; weight; force;
   importance; impressiveness.

Source : WordNet®

weightiness
     n : the property of being comparatively great in weight; "the
         heaviness of lead" [syn: {heaviness}] [ant: {lightness}]