The exact definition may vary between manufacturers, but generally the term denotes, there are no original manufacturer splices in a given length of product.
For example 3M ribbon cable can come with up to 3 splices per 100 foot length. If you need a length of cable that’s guaranteed to not have splices make sure to check the datasheet for the Splice Free part number callout. The 3M HF365 series calls this out using the SF suffix at the end of their part number.
Example datasheet for the :
