If a product consistently requires a new description each time it is sold, you can set it to be a miscellaneous item. "Is Miscellaneous Item" is an option on the part details page.
- Office > Inventory > Products > Manage Products; search for the item and click its part number to view part details
This option will prompt an automatic popup in Point of Sale when the item is placed on an invoice, with a blank description field ready for entry.