kickback

n. 1. recoil, of a gun or machine, as in older automobile engines when started by turning a crank. [ PJC ]

2. A secret, and usually illegal, payment, by a recipient of money paid for goods or services, to a facilitator of the transaction, of a portion of that money; specifically, any portion of a gain made by the seller in a commercial transaction which is returned surreptitiously and illegally to a person (such as a purchasing agent) who authorized or recommended the purchase. It is generally considered a form of bribe. [ PJC ]