Definitions by HNZ

Boomerang Money 

Buying a gift for someone with their own money.

Charging Christmas presents for your parents to a credit card they pay for.

"Thank you for the gifts they are so nice."
"Your Welcome. Its all boomerang money anyway."

Also "treating" your roommates to pizza or beer with money they left out on the counter earlier and you claimed.

Boomerang Money by HNZ December 8, 2010