What does it mean?

Variable weight

Variable weight products include deli items, which are priced based on an estimate of the product weight, then adjusted upon shipment to reflect the actual product weight.

This means that the amount you're charged will change slightly by the time your item is shipped. These items will display the message "Variable weight items are priced based on an estimate of the product weight. Your final invoice at delivery will reflect pricing for the actual weight of the item".