What does pile up mean?
pile up
Definition
To push or tip loose material such as sand, gravel or snow together into a big heap.
Example sentences
The wheel loader's piled up the gravel against our garden wall, and now there's a crack running right down it.
By February they'd piled up so much snow in the parking lot that it was taller than the bus shelter.
By February they'd piled up so much snow in the parking lot that it was taller than the bus shelter.