trade-in [ trād] ′in′
noun a used car, appliance, etc. given or taken as part payment in the purchase of a new one a transaction involving a trade-in the valuation allowed by the seller on a trade-in Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
noun Merchandise accepted as partial payment for a new purchase. A transaction involving such merchandise. The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved. trade-in - Phrases/Idioms
Give or sell an old or used item and apply the value or proceeds to a new item. For example,
Some people prefer to trade in their old car to the dealer, but we feel we'll do better by simply selling it. [First half of 1900s] The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.