late 14c., "full of pores," from Old French poros (14c., Modern French poreux), from Medieval Latin porosus; or directly from Latin porus "an opening" (see pore (n.)). Figurative use from 1640s.
compacting the soil to make it less porous
the partly porous walls of our digestive system
our unfenced and largely unpoliced border inevitably has been very porous