having spaces or holes through which liquid or air may pass.

Merriam-Webster Online Dictionary
porous (adjective)
a) possessing or full of pores
b) containing vessels - hardwood is porous
a) permeable to fluids
b) permeable to outside influences
capable of being penetrated - porous national boundaries
porous (Wikipedia)

Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure the "accessible void", the total amount of void space accessible from the surface (cf. closed-cell foam). There are many ways to test porosity in a substance or part, such as industrial CT scanning. The term porosity is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, hydrology, earth sciences, soil mechanics and engineering.

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