A Top of the Rack or (TOR) switch is a small port count switch that sits on the very top or near the top of a Telco rack you see in Data Centers or Co-location facilities.
Cisco and Brocade as well as other OEM (Original Equipment Manufacturers) describe their new FCoE (Fiber Channel over Ethernet) switches to be "Top of the Rack" thus differentiating them as being small low-cost low port count switches easy to deploy and manager etc.