Extrusion is the process of pushing or forcing material through a shaped opening to create a specific form. Think of squeezing toothpaste from a tube: the paste comes out in a long, round shape because of the circular opening. That's extrusion in its simplest form.

Manufacturers use extrusion to make countless everyday objects. When you see aluminum window frames, plastic pipes, or even certain snack foods, you're looking at extruded products. The material (often plastic, metal, or clay) starts as a soft mass, gets pushed through a die (a specially shaped opening), and comes out in a continuous length with that exact shape. A machine might extrude melted plastic through a star-shaped die to create star-shaped pieces, or push aluminum through a rectangular die to make door frames.

Volcanic lava creates extrusive rock when it’s forced out onto the Earth's surface. In geology, an extrusion can mean rock or lava that has been pushed up from below.

You can see extrusion at work in a 3D printer, which extrudes thin streams of melted plastic to build objects layer by layer. Even Play-Doh toys that push dough through shaped holes demonstrate extrusion. It's a powerful manufacturing technique because once you create the right die, you can produce thousands of identical shapes quickly and efficiently.