What does PILE mean?

noun

1. a collection of objects laid on top of each other
2. (often followed by `of') a large number or amount or extent“a batch of letters”
3. a large sum of money (especially as pay or profit)“she made a bundle selling real estate”
4. fine soft dense hair (as the fine short hair of cattle or deer or the wool of sheep or the undercoat of certain dogs)
5. battery consisting of voltaic cells arranged in series; the earliest electric battery devised by Volta
6. a column of wood or steel or concrete that is driven into the ground to provide support for a structure
7. the yarn (as in a rug or velvet or corduroy) that stands up from the weave“for uniform color and texture tailors cut velvet with the pile running the same direction”
8. a nuclear reactor that uses controlled nuclear fission to generate energy