The Collaborative International Dictionary of English v.0.48:
Porosity \Po*ros"i*ty\, n. [Cf. F. porosit['e].] The quality or state of being porous; -- opposed to density. [1913 Webster]WordNet (r) 3.0 (2006):
porosity n 1: the property of being porous; being able to absorb fluids [syn: porosity, porousness] [ant: solidity, solidness]