pile up

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

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

   • 1898, J. Meade Falkner, Moonfleet, Chapter 4

     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.

   The requests piled up while she was away.

• (form a pile) heap up; see also Thesaurus:pile up
• (accumulate) head up

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

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