diffuseness

from WordNet (r) 3.0 (2006)

diffuseness
    n 1: the spatial property of being spread out over a wide area
         or through a large volume

from The Collaborative International Dictionary of English v.0.48

Diffuseness \Dif*fuse"ness\, n.
   The quality of being diffuse; especially, in writing, the use
   of a great or excessive number of word to express the
   meaning; copiousness; verbosity; prolixity.
   [1913 Webster]