impermeable

American  

[im-pur-mee-uh-buhl] / ɪmˈpɜr mi ə bəl /

adjective

1. not permeable; impassable.

2. Chemistry, Geology. (of porous substances, rocks, etc.) not permitting the passage of a fluid through the pores, interstices, etc.

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impermeable British  

/ ɪmˈpɜːmɪəbəl /

adjective

1. (of a substance) not allowing the passage of a fluid through interstices; not permeable

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impermeable Scientific  

/ ĭm-pûr′mē-ə-bəl /

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.

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Other Word Forms

• impermeability noun
• impermeableness noun
• impermeably adverb

Etymology

Origin of impermeable

From the Late Latin word impermeābilis, dating back to 1690–1700. See im- ², permeable

Compare meaning

How does impermeable compare to similar and commonly confused words? Explore the most common comparisons:

• permeable vs. impermeable

Explanation

If you have a waterproof raincoat, you could say that your coat is impermeable to the rain. Something that is impermeable does not allow water or liquid to pass through it. Made up of the prefix im-, meaning “not,” and the adjective permeable, meaning “allowing to pass through,” impermeable is used in much the same way as impervious or impenetrable. However, more so than these words, impermeable is especially associated with liquids and is often used in a scientific or technical context. Some gadgets, like waterproof watches and underwater cameras, are designed to be impermeable.

Example Sentences

Although scientists once believed that the placenta was a tight, impermeable barrier separating mother and child, that’s not true.

From The Wall Street Journal • Nov. 4, 2025

Municipal wells typically draw drinking water from hundreds of feet underground, often tapping into aquifers that lie beneath impermeable clay and silt layers called aquitards.

From Los Angeles Times • Feb. 13, 2025

It is the fantasy of an impermeable barrier that allows one’s purity to remain unsullied.

From Salon • Oct. 17, 2024

Prato demonstrated the method earlier this week outside the emergency department of Valleywise Health Medical Center in Phoenix, packing ice cubes inside an impermeable blue bag around a medical dummy representing a patient.

From Seattle Times • Jun. 4, 2024

But it is illusion to think that there is anything fragile about the life of the earth; surely this is the toughest membrane imaginable in the universe, opaque to probability, impermeable to death.

From "The Lives of a Cell" by Lewis Thomas