1) Article given in part payment 2) Car deal component 3) Car deal part 4) Car lot transaction 5) Car price factor 6) Car price reducer 7) Car sale component 8) Common car sale component 9) Down payment 10) Down payment alternative 11) Kind of allowance 12) New car price offset 13) Old car 14) Old car, often 
A vehicle that is currently owned by the purchaser of a new or used vehicle from a dealer and that is exchanged for the newly purchased vehicle in order to reduce its net price.
[n] - an item of property that is given in part payment for a new one
noun an item of property that is given in part payment for a new one