Boot

Boot

Cash or other property added to an exchange or transaction in order to make the value of traded goods equal.

Notes:

For example, when you trade in an older car (and cash) for a new model, the cash you pay in addition to your older car is the boot. In fact, you still hear people say things like "I'll throw in the warranty to boot," when referring to a sweetener for a deal.

See also: Barter, Sweetner