Large sums of money paid or reimbursed by a grandfather to his children or grandchildren for extravagent or unnessary purchases such as vacations, vehicles, clothes, and entertainment.

"Bumpa" being a common term used to refer to a grandfather and "bucks" being a common slang term for money.
They rented bikes for 5 days and used them only one day, but they don't care, they paid for the bike rentals with bumpa-bucks.
by Harijan July 30, 2009
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