1.Definition: able to absorb fluids

"The partly porous walls of our digestive system", "Compacting the soil to make it less porous"

2.Definition: allowing passage in and out

"Our unfenced and largely unpoliced border inevitably has been very porous"

Related Adjective(s):holey

3.Definition: full of pores or vessels or holes

Related Adjective(s):poriferous