The idea that microprocessor instructions could be more directly applied to hardware by specifying only the data transport. This is contrasted with specifying an operation and one or more pieces of data, or Operation-triggered architectures. The processors people are most familiar with are of the OTA variety - they typically require at least 2 data transports to get operands into the ALU and a result out. In TTA only the source and destination of the transport are specified, no operation is needed. The benefits of TTA design include a faster design cycle (it is very modular), several compiler optimizations are helped by the design, and it reduces complexity. To achieve its functionality, some of the "registers" are Function Units which carry out some logical operation, which is triggered by the data being moved into it.
For more info