pile·up 
/ˈpajəlˌʌp/ noun
plural pile·ups /ˈpajəlˌʌp/ noun [count] 1 : an accident in which several or many vehicles crash into each other
▪ A five-car pileup slowed traffic. 2 : a large amount of something that has increased gradually over a period of time
▪ a pileup of debt — see also pile up at 2pile
▪ A five-car pileup slowed traffic.
▪ a pileup of debt — see also pile up at 2pile
