igneous
Americanadjective
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Geology. produced under conditions involving intense heat, as rocks of volcanic origin or rocks crystallized from molten magma.
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of, relating to, or characteristic of fire.
adjective
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(of rocks) derived by solidification of magma or molten lava emplaced on or below the earth's surface Compare sedimentary metamorphic
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of or relating to fire
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Relating to rocks or minerals formed by the cooling and hardening of magma or molten lava. Basalt and granite are examples of igneous rocks.
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Relating to the processes, such as volcanism, by which such rocks and minerals form.
Other Word Forms
Etymology
Origin of igneous
First recorded in 1655–65; from Latin igneus “fiery, on fire, burning,” equivalent to igni(s) “fire” + -eus -eous. Ignis is the Latin form of the Proto-Indo-European egni-s, ogni-s, one of the Proto-Indo-European words for “fire,” and it is closely related to Slavic ( Polish ) ogień (inflectional stem ogni- ) and to Sanskrit agni- Agni ( def. ); see fire ( def. )
Explanation
You might remember this one from earth science class. An igneous rock is one that forms through intense, fiery heat — usually in a volcano. It starts out molten (so hot it melts into liquid), then solidifies as it cools. So, it’s rock that has “ignited.” Igneous comes from the Latin ignis, "fire." Granite and basalt are good examples of igneous rock that started out as blazing hot lava and morphed into harder stuff as their temperature dropped. FYI, the other main types of rocks are sedimentary and metamorphic and, technically, you could use igneous to describe other things that are rare or fiery, but it would sound pretty stilted and most people wouldn’t know what you meant.
Vocabulary lists containing igneous
In A Sedimental Mood: Rock and Gem Vocabulary
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Physical Geography - Middle School
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Elements of the Universe: Ign, Igni ("Fire")
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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.
The molten material solidified into rare igneous rocks known as carbonatites, locking valuable metals into the crust.
From Science Daily • Jan. 23, 2026
Heavy rare earths are formed over millions of years, as rainfall weathers igneous rocks, breaking them down and leaving elements concentrated near the surface.
From Barron's • Dec. 21, 2025
In the process they learned that “a mid-crust composed of fractured igneous rocks saturated with liquid water best explains the existing data.”
From Salon • Aug. 14, 2024
Now if you were awake in high school science class, you’re thinking, igneous rock: volcanic lava.
From Los Angeles Times • May 3, 2024
Green and dark-green are the prevalent tints of the hornfelses produced by the alteration of igneous rocks.
From Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 6 "Home, Daniel" to "Hortensius, Quintus" by Various
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
