[im-pur-mee-uh-buh l]
See more synonyms for impermeable on
  1. not permeable; impassable.
  2. Chemistry, Geology. (of porous substances, rocks, etc.) not permitting the passage of a fluid through the pores, interstices, etc.

Origin of impermeable

From the Late Latin word impermeābilis, dating back to 1690–1700. See im-2, permeable
Related formsim·per·me·a·bil·i·ty, im·per·me·a·ble·ness, nounim·per·me·a·bly, adverb
Can be confusedimpermeable impervious Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for impermeable


  1. (of a substance) not allowing the passage of a fluid through interstices; not permeable
Derived Formsimpermeability or impermeableness, nounimpermeably, adverb
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

Word Origin and History for impermeable

1690s, from French imperméable, from Late Latin impermeabilis, from assimilated form of in- "not, opposite of" (see in- (1)) + permeabilis (see permeable).

Online Etymology Dictionary, © 2010 Douglas Harper

impermeable in Medicine


  1. Impossible to permeate; not permitting passage.
Related formsim•per′me•a•bili•ty null n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

impermeable in Science


  1. Relating to a material through which substances, such as liquids or gases, cannot pass. Some substances, such as some types of contact lenses, are permeable to gas but impermeable to liquid.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.