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[pawr-uh s, pohr-] /ˈpɔr əs, ˈpoʊr-/
full of pores.
permeable by water, air, etc.
Origin of porous
1350-1400; Middle English, variant of porose < Medieval Latin porōsus. See pore2, -ous
Related forms
porously, adverb
porousness, noun
nonporous, adjective
nonporousness, noun
unporous, adjective
unporousness, noun
2. penetrable, pervious, sievelike, riddled. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for porous
Contemporary Examples
Historical Examples
  • The soft layers are porous, and permit the diffusion of the acid from plate to plate.

  • Hanging from one of the sticks that supported the tent was a porous jar of water.

    At Aboukir and Acre George Alfred Henty
  • Papillate -us: a surface with small elevations which are porous at tip.

  • It should be porous in a high degree—whether in winter weight or summer weight.


    William H. Dooley
  • The vein was porous and water was constantly trickling out of it.

    Diggers in the Earth Eva March Tappan
British Dictionary definitions for porous


permeable to water, air, or other fluids
(biology, geology) having pores; poriferous
easy to cross or penetrate: the porous border into Thailand, the most porous defence in the league
Derived Forms
porously, adverb
porousness, noun
Word Origin
C14: from Medieval Latin porōsus, from Late Latin poruspore²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for porous

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.

Online Etymology Dictionary, © 2010 Douglas Harper
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porous in Medicine

porous po·rous (pôr'əs)

  1. Full of or having pores.

  2. Admitting the passage of gas or liquid through pores.

po'rous·ness n.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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porous in Science
Having many pores or other small spaces that can hold a gas or liquid or allow it to pass through.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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