OBO
Or Best Offer. The seller is open to receiving offers below the listed price. On eBay, this is a formal feature where buyers submit offers that auto-accept or auto-decline based on thresholds you set.
Where you'll see this
This term is commonly used on:
ebayfacebook-marketplace
Put this into practice
Shopfront handles the hard parts of crosslisting and inventory sync so you can focus on finding and selling.