Definition of pile:
a hair; hence, the fiber of wool, cotton, and the like; also, the nap when thick or heavy, as of carpeting and velvet; a covering of hair or fur
"velvet soft, or plush with shaggy pile. —Cowper"
to drive piles into; to fill with piles; to strengthen with piles; to lay or throw into a pile or heap; to heap up; to collect into a mass; to accumulate; to amass; — often with up; as, to pile up wood