The Collaborative International Dictionary of English v.0.48:
Sparseness \Sparse"ness\, n. The quality or state of being sparse; as, sparseness of population. [1913 Webster]WordNet (r) 3.0 (2006):
sparseness n 1: the property of being scanty or scattered; lacking denseness [syn: sparseness, spareness, sparsity, thinness]