WordWeb Online

1. Multiple collisions of vehicles

1. Collect or gather
   "The work keeps piling up"
   - accumulate, cumulate, conglomerate, gather, amass
    
2. Arrange into piles or stacks
   "She piled up her books in my living room"
   - heap up, stack up
    
3. Get or gather together
   - roll up, collect, accumulate, amass, compile, hoard

Derived forms: piles up, pileups, piling up, piled up

Type of: collect, collision, garner, gather, hive away, increase, lay in, pull together, put in, salt away, stack away, stash away, store

Encyclopedia: Pileup