As Giuseppe mentions, "fabric" is often the term for a cross bar matrix. A cross bar allows every end point full bandwidth to any other end point without sharing the bandwidth.
For instance ports 1 and 2 could use their maximum bandwidth regardless of what the other ports are doing. However, if both ports 1 and 2 wanted to pass traffic to/from port 3, they would share port 3's fabric connection.
True port-to-port switch fabrics are very expensive, so many switch fabrics group ports that share a larger quanity of bandwidth to the switch fabric. For instance, the original 4500 series provides 6 GB of switch fabric to each slot. Line cards often allocate this fabric bandwidth equally, but the don't have to. An interesting example is the WS-X4418-GB which provide full gig to two ports and the remaining four gig to 16 ports (see table 2 in http://www.cisco.com/en/US/prod/collateral/modules/ps2710/ps5494/product_data_sheet0900aecd802109ea_ps4324_Products_Data_Sheet.html)
The 6500 supports different methods of bandwidth to the slots. It can support a shared 32 gig using its "classic bus" (sup1/sup-32/sup2(w/o optional SFM); 256 gig fabric (sup2 w/SFM or sup720), 1 or 2 8 gig connections to each slot; or 720 gig fabric (sup720), 1 or 2 20 gig connection to each slot. 6500 line cards are designed for these different backplane connections and how and they share the slot's bandwidth between their ports.
Other switch fabric implementions can differ.
