[ mag-muh ]
/ ˈmæg mə /
Save This Word!

Definition of magma

noun, plural mag·mas, mag·ma·ta [mag-muh-tuh]. /ˈmæg mə tə/.
Geology. molten material beneath or within the earth's crust, from which igneous rock is formed.
any crude mixture of finely divided mineral or organic matter.
Chemistry, Pharmacology. a paste composed of solid and liquid matter.
Should you take this quiz on “shall” versus “should”? It should prove to be a quick challenge!
Question 1 of 6
Which form is used to state an obligation or duty someone has?

Origin of magma

1400–50; late Middle English <Latin: dregs, leavings <Greek mágma kneaded mass, salve, equivalent to mag- (base of mássein to knead, press; see mass) + -ma noun suffix of result


mag·mat·ic [mag-mat-ik], /mægˈmæt ɪk/, adjectivemag·ma·tism, noun


lava, magma
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What’s the difference between magma and lava?

Magma is what molten (melted) rock is called when it’s under the earth’s surface. Lava is what molten rock is called when it flows out of a volcano or volcanic vent.

To be clear, in popular use, magma and lava are essentially different names for the same liquid-hot, charred orange ooze—which name is used depends on whether it is above or below the surface.

However, geologists and volcanologists have their reasons for using the two different terms to distinguish between forms of what is the same substance.

Magma doesn’t always become lava—sometimes it cools and solidifies beneath the earth’s surface. Sometimes, it collects in what’s known as a magma chamber. When it does reach the surface, it flows out as lava. The rock that’s formed when it hardens and cools can also be called lava, though this use of the term is uncommon outside of technical, scientific contexts.

The word lava is perhaps the more well-known of the two because that’s the one we see when volcanoes erupt (or when the floor turns into it).

Here is an example of magma and lava used correctly in the same sentence.

Example: Lava began flowing from the volcano three days after scientists detected movement of magma underground.

Want to learn more? Read the full breakdown of the difference between magma and lava.

Quiz yourself on magma vs. lava!

Should magma or lava be used in the following sentence?

The eruption resulted in a steady flow of _____ from the volcano.

How to use magma in a sentence

British Dictionary definitions for magma

/ (ˈmæɡmə) /

noun plural -mas or -mata (-mətə)
a paste or suspension consisting of a finely divided solid dispersed in a liquid
hot molten rock, usually formed in the earth's upper mantle, some of which finds its way into the crust and onto the earth's surface, where it solidifies to form igneous rock

Derived forms of magma

magmatic (mæɡˈmætɪk), adjectivemagmatism, noun

Word Origin for magma

C15, from Latin: dregs (of an ointment), from Greek: salve made by kneading, from massein to knead
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

Medical definitions for magma

[ măgmə ]

A mixture of finely divided solids with enough liquid to produce a pasty mass.
A suspension of particles in a liquid, such as milk of magnesia.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for magma

[ măgmə ]

Plural magmata (măg-mä) or magmas
The molten rock material that originates under the Earth's crust and forms igneous rock when it has cooled. When magma cools and solidifies beneath the Earth's surface, it forms what are known as intrusive rocks. When it reaches the Earth's surface, it flows out as lava and forms extrusive (or volcanic) rocks.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for magma


Molten rock usually located deep within the mantle of the Earth that occasionally comes to the surface through cracks in the mantle or through the eruption of volcanoes.

notes for magma

When magma cools and solidifies, it forms igneous rock, of which lava is one type.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.