The Collaborative International Dictionary of English v.0.48:

Imporosity \Im`po*ros"i*ty\, n. [Perf. im- not + porosity: cf.
   F. imporosit['e].]
   The state or quality of being imporous; lack of porosity;
   compactness. "The . . . imporosity betwixt the tangible
   parts." --Bacon.
   [1913 Webster]