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mid-15c., "dregs," from Latin magma "dregs of an ointment," from Greek magma "thick unguent, ointment," from root of massein "to knead, mold," from PIE *mag- "to knead" (see macerate). Geological meaning "molten rock" is 1859. Related: Magmalic.
magma mag·ma (māg'mə)
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.
Plural magmata (māg-mä'tə) 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.