'pile up' definitions:

Definition of 'pile up'

From: WordNet
verb
Collect or gather; "Journals are accumulating in my office"; "The work keeps piling up" [syn: accumulate, cumulate, conglomerate, pile up, gather, amass]
verb
Arrange into piles or stacks; "She piled up her books in my living room" [syn: pile up, heap up, stack up]
verb
Get or gather together; "I am accumulating evidence for the man's unfaithfulness to his wife"; "She is amassing a lot of data for her thesis"; "She rolled up a small fortune" [syn: roll up, collect, accumulate, pile up, amass, compile, hoard]

Synonyms of 'pile up'

From: Moby Thesaurus