[n] molten rock in the earth's crust
\Mag"ma\, n. [L., fr. Gr. ?, fr. ? to squeeze, knead.]
1. Any crude mixture of mineral or organic matters in the state of a thin paste. --Ure.
2. (Med.) (a) A thick residuum obtained from certain substances after the fluid parts are expressed from them; the grounds which remain after treating a substance with any menstruum, as water or alcohol. (b) A salve or confection of thick consistency. --Dunglison.
3. (Geol.) (a) The molten matter within the earth, the source of the material of lava flows, dikes of eruptive rocks, etc. (b) The glassy base of an eruptive rock.
4. (Chem.) The amorphous or homogenous matrix or ground mass, as distinguished from well-defined crystals; as, the magma of porphyry.