Paving made to look old on purpose, for cosmetic reasons. Stone that is tumbled is deliberately processed to give it a weathered finish and appear older than it is.
As the name suggests, tumbling originally involved passing the stone through a rotating drum supported with granite, sand and water. This made the slabs strike each other, softening the lines of the stone and rubbing away at the corners and edges. However, this old-fashioned way had a high incidence of breakage and has been replaced by a newer method.
Nowadays, tumbled paving slabs are created by placing the paving slabs in a vibrating vat filled with aggregate or small loose stones to soften the edges and corners. This process has the same end result but with much less wastage.