1. Squeezing out by applying pressure: There was an unexpected extrusion of toothpaste from the bottom of the tube.

Grace turned a bottle upside down and suddenly an extrusion of ketchup spilled out onto her plate.

2. Something that bulges out, is protuberant, or projects from a form: Little Timmy wondered about the extrusion of his mother’s tummy; so, she told him that she was pregnant and was expecting a baby girl!
3. Something formed by forcing semisoft material through a specially shaped mold or nozzle: An extrusion takes place when a partly finished length of metal is thrust through a die to create a metal object; such as, a rod or a pipe.
4. An igneous rock formed by the emission of molten material or magma through cracks in the earth's surface where it forms a lava flow and solidified igneous rock: At the museum of natural history, the group of students were shown pieces of extrusions which exist in certain outer layers of the earth.