pile up (third-person singular simple present piles up, present participle piling up, simple past and past participle piled up)

1. (transitive) To form a pile, stack, or heap.

   Synonyms: Thesaurus:pile up

   Coordinate term: pile on

   The kids piled up their boots and coats by the back door.

   • [1898], J[ohn] Meade Falkner, Moonfleet, London; Toronto, Ont.: Jonathan Cape, published 1934, →OCLC ↗:

     And still the hours passed, and at last I knew by the glimmer of light in the tomb above that the sun had risen again, and a maddening thirst had hold of me. And then I thought of all the barrels piled up in the vault and of the liquor that they held; and stuck not because 'twas spirit, for I would scarce have paused to sate that thirst even with molten lead.

   • 1977, Agatha Christie, chapter 2, in An Autobiography, part II, London: Collins, →ISBN:

     If I close my eyes I can see Marie today as I saw her then. Round, rosy face, snub nose, dark hair piled up in a chignon.

2. (idiomatic, intransitive) To collect or accumulate, as a backlog.

   Synonyms: head up

   The requests piled up while she was away.

• French: amonceler, empiler
• German: stapeln
• Italian: impilare, impilarsi (reflexive form)
• Portuguese: amontoar, empilhar
• Russian: нагроможда́ть
• Spanish: acumular, arrumar, apilar

• French: amonceler
• Portuguese: amontoar
• Russian: нака́пливаться
• Spanish: amontonarse