what does "pool their change"mean?
Discovering that their waitress had vanished, they had pooled their change, flung it on the table, and raced out, passing Colonel McNally who had eaten early and was waiting patiently at the cashier's desk.

Question

Answer

"Pooled their change" means they put whatever money they had into a pile or a "pool". 
For example, my friends and I pooled our money so we could get a pizza for friday night.

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