Refurbished mattresses are also known as reconditioned or remanufactured, but it’s just a fancy term for used. The only difference between a refurbished and used mattress is refurbished models are sanitized and sometimes repaired.
You can commonly find refurbished mattresses at thrift stores, charities, and secondhand furniture stores. While a refurbished bed is a bit better than a used one, it’s usually not worth buying.