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porous

American  
[pawr-uhs, pohr-] / ˈpɔr əs, ˈpoʊr- /

adjective

  1. full of pores.

  2. permeable by water, air, etc.

    Synonyms:
    riddled, sievelike, pervious, penetrable

porous British  
/ ˈpɔːrəs /

adjective

  1. permeable to water, air, or other fluids

  2. biology geology having pores; poriferous

  3. easy to cross or penetrate

    the porous border into Thailand

    the most porous defence in the league

"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

porous Scientific  
/ pôr′əs /
  1. Having many pores or other small spaces that can hold a gas or liquid or allow it to pass through.


Other Word Forms


Etymology

Origin of porous

First recorded in 1350–1400; Middle English, variant of porose, from Medieval Latin porōsus; see pore 2, -ous


Explanation

If something is full of tiny holes or openings, you can describe it as porous. A sponge is porous, and if the border between countries is open for anyone to cross easily, it too can be called porous. You can see the word pore — meaning "a tiny opening" — in porous. When potters make a mug, they use special glazes to seal the porous clay, which otherwise would absorb the liquid you put in the mug. This meaning has expanded so porous can describe any barrier that allows easy passage in and out, like the porous border between two countries that allows residents to move easily between them.

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Vocabulary lists containing porous

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

The water sinks into porous soil and replenishes the groundwater.

From Los Angeles Times ● Sep. 26, 2026

These scaffolds consist of individual hydrogel microparticles that assemble into a porous structure.

From Science Daily ● Sep. 4, 2026

Ms. Cline creates a porous mental tapestry of frayed gaps and vivid imagery.

From The Wall Street Journal ● Sep. 1, 2026

Pesticides prohibited in Kenya are sometimes smuggled across this porous border with Tanzania and used in farms within the Amboseli area, where elephants live near human settlements and are known to raid farms for food.

From BBC ● Aug. 24, 2026

Such arguments depended on analogies: comparing the skin, for example, to porous earthenware.

From "The Invention of Science" by David Wootton

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