To extrude means to push or squeeze a material through an opening to create a specific shape. Think of squeezing toothpaste from a tube: the paste is forced through the small opening and comes out in a long, round ribbon. That's extrusion.

Factories use extrusion to manufacture countless products. Plastic pipes, aluminum window frames, and even some types of pasta are all extruded. The material (often heated to make it soft) gets pushed through a specially shaped hole called a die, and whatever shape the die has becomes the shape of the product. It's like using a cookie press or frosting bag: the dough or frosting takes the shape of the opening as it's forced through.

In 3D printing, plastic filament is extruded through a tiny heated nozzle, building objects layer by layer. Volcanoes extrude lava when molten rock is forced up and out onto the surface. The word emphasizes the pushing through action rather than just flowing or pouring. When something is extruded, pressure forces material through an opening to give it form.