General synonyms:
* Used
* Pre-owned
* Previously owned
* Resale
* Refurbished (if the item has been repaired or improved)
* Vintage (for older items)
* Antique (for very old and valuable items)
More specific synonyms:
* Hand-me-down (for clothing or other items passed down from one person to another)
* Consignment (for items sold through a consignment shop)
* Thrift store (for items bought from a thrift store)
* Junk (for items that are old, broken, or of low quality)
* Salvage (for items that have been rescued from a disaster)
* Recycled (for items that have been made from used materials)
The best word to use will depend on the specific situation.