1
: a gelatinous or mucinous substance found normally in the thyroid and also in diseased tissue
2
a
: a substance that consists of particles dispersed throughout another substance which are too small for resolution (see resolution sense 6a) with an ordinary light microscope but are incapable of passing through a semipermeable membrane
b
: a mixture consisting of a colloid together with the medium in which it is dispersed
smoke is a colloid
colloidally
adverb
Examples of colloid in a Sentence
Recent Examples on the Web
The safety effect comes from a colloid, a suspension of tiny solid particles in a liquid.
—
Bojan Stojkovski, Interesting Engineering, 6 Sep. 2025
On Wednesday, May 14, the Hollywood Medium star, 29, revealed on Instagram that he'd been diagnosed with a colloid tumor near the center of his brain, which had required surgery to remove it.
—Becca Longmire, People.com, 15 May 2025
In colloids as in biofilms, these interactions are governed by two opposing forces.
—Carrie Arnold, Quanta Magazine, 21 Apr. 2025
Healthcare providers use colloid fluids for people with severe dehydration or fluid loss.
—Rachael Zimlich, Bsn, Rn, Verywell Health, 23 Sep. 2024
Bluing is not a dye, but rather a colloid of blue iron salt suspended in water.
—Jolie Kerr, Better Homes & Gardens, 18 Sep. 2024
Shining a laser light through a gold colloid mixture produces the Faraday-Tyndall Effect.
—Jennifer Ouellette, Ars Technica, 26 Dec. 2023
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Bojan Stojkovski, Interesting Engineering, 6 Sep. 2025
On Wednesday, May 14, the Hollywood Medium star, 29, revealed on Instagram that he'd been diagnosed with a colloid tumor near the center of his brain, which had required surgery to remove it.
—Becca Longmire, People.com, 15 May 2025
In colloids as in biofilms, these interactions are governed by two opposing forces.
—Carrie Arnold, Quanta Magazine, 21 Apr. 2025
Healthcare providers use colloid fluids for people with severe dehydration or fluid loss.
—Rachael Zimlich, Bsn, Rn, Verywell Health, 23 Sep. 2024
Bluing is not a dye, but rather a colloid of blue iron salt suspended in water.
—Jolie Kerr, Better Homes & Gardens, 18 Sep. 2024
Shining a laser light through a gold colloid mixture produces the Faraday-Tyndall Effect.
—Jennifer Ouellette, Ars Technica, 26 Dec. 2023
Cite this Entry
“Colloid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/colloid. Accessed 31 Oct. 2025.
Copy CitationKids Definition
colloid
noun
col·loid
ˈkäl-ˌȯid 
: a very finely divided substance which is scattered throughout another substance
also
: a mixture consisting of such a substance together with the substance in which it is scattered (as in smoke, gelatin, or marshmallow)
Medical Definition
colloid
noun
col·loid
ˈkäl-ˌȯid
1
: a gelatinous or mucinous substance found in tissues in disease or normally (as in the thyroid)
2
a
: a substance consisting of particles that are dispersed throughout another substance and are too small for resolution with an ordinary light microscope but are incapable of passing through a semipermeable membrane
b
: a mixture (as smoke) consisting of a colloid together with the medium in which it is dispersed
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