1530s, from Latin extrusionem (nominative extrusio), noun of action from past participle stem of extrudere, from ex- "out" (see ex-) + trudere "to thrust, push," from PIE *treud- "to press, push, squeeze" (see threat).
The emission of lava onto the surface of the Earth. ◇ Rocks that form from the cooling of lava are generally fine-grained (because they cool quickly, before large crystals can grow) and are called extrusive rocks. Compare intrusion.
The process of making a shaped object, such as a rod or tube, by forcing a material into a mold.